Hi!
Been using Linux since 2009 but this is the first time I've received the error 'format of the disc image could not be identified. Please set it manually.' when selecting an image to burn using Brasero. I've tried 24.04.02 and 25.04, both ubuntu-mate images yet both give the same error.
What could cause the error and why would I need to set the image manually?
My work around is to use an old DVD with 22.04 on it and keep upgrading from there.
Fubbery
Hi, @Fubbery and welcome to the Ubuntu MATE Community!
wget https://cdimage.ubuntu.com/ubuntu-mate/releases/noble/release/ubuntu-mate-24.04.2-desktop-amd64.iso
#verify iso
sha256sum ubuntu-mate-24.04.2-desktop-amd64.iso
ec1399cf90678c29ee1f80055826b21a3d90f59d50d154e5ea70b1931ce909c9 ubuntu-mate-24.04.2-desktop-amd64.iso
Last time I used a DVD was 10+ years ago so I cannot help there. I always burn the iso to a usb and let my pc boot from the usb to install.
I use Applications | Accessories | Disks to restore the image (.iso) to the usb.
You might want to look at what Google Search AI suggests for
linux disk image repair iso
Apparently, GNOME Disks or Boot Repair can each help you "recover" the ISO image, after which you can create your own image.
I just booted up a questing system on an secondary box of mine that has a DVD writer in it, installed brasero and selected Ubuntu MATE 24.04.2 ISO for writing without issue, and whilst I didn't have a local copy of Ubuntu MATE 25.04 accessible, it had no issue with Xubuntu 25.04 (same installer & will be pretty close), Lubuntu 25.04 (different installer & somewhat different ISO) or Ubuntu Desktop 25.04.
You didn't specify what OS/release you're using, so I didn't have anything specific to try, thus selected the first Ubuntu release I had listed in grub (which is why questing). I didn't write an image as you reporting getting the error on selection.
I doubt there would be an issue if I used a different release though, whilst there is less testing done now on DVD/optical media, its still in the check list for Canonical/Ubuntu Desktop team last I heard. I may not have written an ISO to optical in some time; and that was to explore issues reported after a LTS release, but I'm very aware that optical drives are now getting rather old & thus prone to failure (that doesn't seem to fit your issue though I'll admit!).
Ubuntu hasn't created the ISO for optical install since the 20.04 release though; as there are very few people using it (it's very much optimized now for usage on cloud/disk or flash media)
Sorry, Chris, but that statement is making me "freak out" a bit. My last install involved UM 22.04 from live disk.
Are you suggesting that UM 24.04 and later will not be available for ISO targetted for DVD?
Or are you only referring to the basic UbuntuGNOME or Ubuntu Server versions?
In the kinetic (22.10) cycle the ISOs were altered so all architectures booted the same for a given release; as well as other changes, which included background self-checking of media. A decision was made (based on the tiny number of logged installs) to do that in a manner that suited flash media which allow checking files individually, which is inefficient on storage media such as optical where drives need to alter spin speed.
Optical media should still work, but the self-check & some other decisions are efficient for flash but not optical; this decision was made back in 2020.
No change that I'm aware of has happened since, so there is no change in 24.04 & later, and the change impacted all Ubuntu ISOs, thus flavors too.
When this change occurred; there was a number of bug reports filed, as some older drives handled the media checks much worse than newer drives.. for the older drives the fix is just to wait until self-check completes, as if you try and install or use the system whilst media check is still running, chance of 'timeout' errors increased, these media-timeout errors were sometimes misread by running apps; errors were only appearing on older optical drives though it was noted
Can you clarify, or share any insights, as to what "tiny number of logged installs" means?
Is there any preconceived notion that the Optical drive is a defunct technology which must be phased out or for which specific support is no longer within the "scope" of Ubuntu?
After installing a Ubuntu ISO (some variation based on product/release), the user is asked if they'd like to provide some details of the install, which include details of your hardware (RAM, install media; disk capacity etc), install options and country.of.install (detail that could identify you is very limited; its hardware details/capacities that are mostly sought) these are uploaded & logged if the user accepts it. This detail provides a lot of the information to which I was referring (and the user can view this detail prior to upload).
Results of some of that have been published at various times (in summary anyway, if I recall correctly Will Cooke published the most), let alone surveys of users & those results to provided (eg. Ubuntu 20.04 survey results | Ubuntu)
QA is still done with Ubuntu Desktop/Server ISOs with optical media; but due to the tiny number of users (within margin of error for statistics) QA testing is minimal.
I know I've always answered yes to those feedbacks from installs, so I guess I must be part of that "margin of diminishing returns that will be extinguished" because there are so few of us "optical-based" users! 
I like having a known frozen, non-modifiable Live ISO image as a failsafe. Sure, flash drive has its attractions, but not my preferred way of "service delivery".
The problem is almost no one puts a CD/DVD writer into a desktop or laptop anymore. You can buy CD/DVD writer/players with USB drives for low cost, but USB drives have gained the most popularity. I still have CD/DVD drives, but it gets harder and harder to find the CDs and DVDs to buy.
As I think it's weird to burn DVD to test Ubuntu when USB exist since many years, I disagree about the use case of DVD. I burn DVD every year, to backup my datas, photos and videos. Because DVD, fine stored, it's the only support can pass decades without problem. Better support to let memories digital datas for our kids. In comparison, I backup also on external drive each year. But, I need to replace it every 6/8 years haha.
Because DVD, fine stored, it's the only support can pass decades without problem
That's not proven, by the way. Do you remember when HDD manufacturers were claiming 10,000 years MTBF (mean time between failure)? Meant to convey confidence in the storage media, the truth was that hard disk failures were (are?) routine and more frequent than expected. And who had been able to measure 10,000 years, anyway? Optical discs are susceptible to hairline scratches, cracks and even overexposure.
I've learned the most confident backup strategy involves multiple mediums (and no, the "cloud" is not the panacea everyone thinks it is).
The cost of a DVD disk vs the cost of a USB stick is the deciding point for me!
I don't have money to throw away for a single-use "burn" of an ISO on USB stick.
I'm not sure where you are, but Amazon lists
So, I cheated. I used the lowest cost CD/DVD prices, but went for a name band USB (SanDisk). I found 256Gb thumb drives for as low as US$9. I wouldn't trust them, though. You can also buy packs of 4Gb thumb drives but they're less economical.
In any event, I have several multi-USB (type A and C combined) thumb drives that make moving between devices a snap (no external drive needed), so I can copy/back up what I need easily.
Thank you, Fred. I appreciate what you were trying to do, namely compare prices per GB for the various formats.
Since my goal is not backups,
What is relevant is the cost of one "burn", which does not allow reuse of the sandisk, but makes that sandisk non-reusable, therefor a waste of money for a single-use "burn".
From that perspective, nothing beats optical. 
So, maybe it's me. Help me understand. Are you saying you want the single burn of an optical disc? If so, I can understand the idea that once burned, an optical disc is "forever," but as I indicated earlier, that isn't really so.
There are write-protectable drives, either through a physical switch, or through software, so if that's your concern, solutions exist.
Much like floppy disks (both 5-1/4" and 3-1/2") optical discs are pretty much obsolete these days. I have only one computer that contains an optical drive (I do have an external). Not even my server has a "tray."
I readily concede that the server environment should not be expected to support optical media in this day and age.
The environment of a personal Desktop, however, is an entirely different context, especially in a non-business environment, and the Consumer (End-user) expectations regarding usable lifespan of technologies are drastically different from a Server Admin's, which I was myself during my career, so I can easily flip my hat around and adopt the mind-set that applies to each "role" quite easily.
To give you an insight to my personality, my personal "bi-line" when I worked as sysadmin (close to 15 years) was ...
I'm a Sysadmin with a User attitude!
and my users (about 60 Engineers and Technologists for Nortel residential/business telephone set R&D) really appreciated it!
Yes! I do indeed want a single-burn optical disk for an ISO image.
Noteworthy about optical media from personal experience ...
I discovered to my great misfortune that "forever" in the optical world is only as long as the plastic used for the optical discs. Some were becoming gradually darker over time, to the point that at about 8 years some brands were unreadable and, back then, I was in a panic to migrate the images to better quality discs.
Sandisk-like media are, for my purposes, too expensive. If they sold packs of 50 x 8GB (along with an insertable carrier) for about $20, that would be an acceptable alternative (I have such a carrier for a pair of 16 GB memory chips which I swap periodically in my Android tablet), but such "bulk packs" don't exist.
My issue with USB sticks is that if I "burn" the image of an ISO onto a USB stick that is pre-formatted as ext3/4, any attempts at re-using that USB stick for other purposes has always failed for me. ALL attempts to reformat to fully usable blank USB stick failed!
When I tried to "explode" an ISO into a hard disk directory, modify properties for folders for "chmod u+w,g+w,o+w ...", and corresponding changes for data and executable files, then copied those files onto a USB stick, the resulting stick ws never recognized as a bootable medium for Live or Install.
Hence, my only option to remain with optical for historical "reference" images that are both frozen and bootable.
To that end, if there is
that will guarantee that the resulting "bootable USB stick" is
recognized by the BIOS as a bootable medium (something past attempts never succeeded at), and
ensures the medium can be re-formatted, namely, erasable and re-usable (again, something past approaches and attempts never succeeded at),
I could be persuaded to revisit my reluctant stance, which is based on personal experience with at least 5 failed attempts!
Please don't ask what I previously attempted, because it was 3 years ago and I "tossed" all my scripts and records of the attempts because they were non-functional.
Scientific studies and reliable sources from the canadian conservation Institute
Tests with both accelerated and natural aging show:
CD-R phthalocyanine dye + gold layer: > 100 years
CD-R phthalocyanine + silver alloy: 50–100 years
DVD-R gold layer: 50–100 years
Other types (DVD+R, azo dyes...): 20–50 years, sometimes less
Source
I did backup since 25 years for my personnal data. I use the "rule of 3":
Keep 3 copies of data (DVD, drive, my pc)
Store 2 different types
Keep 1 copy off-site, such as in cloud
@ericmarceau I guess, your issue seem to be in the difficulty of format usb stick. Correct?
The lifespan of a CD can vary depending on factors such as how it’s stored, the quality of the disc, and how frequently it’s used. In general, a well-maintained CD can last for 20-100 years, while lower-quality discs may deteriorate within a decade. Storing CDs in a cool, dry, and dark environment can help prolong their lifespan. Regular usage and exposure to heat, light, and moisture can shorten their longevity.
The best definition of the cloud I have ever heard is: You data on someone else's server.