Hi.
I'll be (hopefully) building a new desktop soon. It'll be an AMD system with a X570 motherboard.
I have a doubt regarding UEFI: in order to access the UEFI BIOS will I have to install Ubuntu Mate with an EFI partition (as I've seen in some tutorials)? If I install without that partition will I be faced with legacy BIOS when accessing it?
The machine will be Ubuntu only with the main SSD with Root and Home partitions.
Thanks.
if the bios option is set to boot UEFI, the install result:
/dev/sda1 /boot/efi
/dev/sda2 /
/dev/sda3 /home
if bios is set to boot legacy, the install result:
/dev/sda1 /
/dev/sda2 /home
HTH
If Ubuntu is installed in EFI mode, it can be detected in one of the following ways:
The / etc / fstab file contains an entry for EFI partition (mount point: / boot / efi). View / etc / fstab results by giving a terminal command
It uses the grub-efi bootloader and not the grub-pc. See it with the result of the command
Open a terminal and execute the following command
[-d / sys / firmware / efi] && echo "Installed in EFI mode" || echo "Installed in Legacy mode"
depending on the results you will know if it is installed on EFI or Legacy.
Source
https://forum.ubuntu-gr.org/viewtopic.php?f=9&t=26244#p278017
I am strongly convinced that BIOS function does not depend on HDD partitioning at all. That is BIOS interface is accessible regardless of an HDD itself or EFI partition presence.
Last week I have installed UM 18.04 on UEFI system. Well, I selected 'Other OS' in BIOS, wiped HDD clean and UM legacy installation has been smooth and successful.
[quote="pavlos_kairis, post:2, topic:21027"]
if the bios option is set to boot UEFI, the install result:
/dev/sda1 /boot/efi
/dev/sda2 /
/dev/sda3 /home
[/quote] With the EFI partition as FAT32 and the others as Ext4 right?
[quote="ugnvs, post:4, topic:21027"]
I am strongly convinced that BIOS function does not depend on HDD partitioning at all.
[/quote] That's my main doubt, could someone confirm please? If I install as legacy can I still access the BIOS as UEFI and tweak it?
Joss,
that's correct ... lsblk -fs will show you that sda1 is vfat and sda2 is ext4.
Not sure I understand the second question ...
You can give it a try to convince yourself. Just disconnect HDD from your system, power cycle it and enter BIOS session.
My own personal experience has been that, at least with Ubuntu, in UEFI mode, grub installation fails. Legacy always worked, and I didn't miss the UEFI features.
Just sayin'.
Basically it doesn't matter which way you install Ubuntu Mate on your new system - you will still need to create a small partition at the beginning for either bios boot - "legacy boot" or efi boot - "uefi boot". If you don't create one of these partitions - the installer will complain and ask you to create one 
I've setup laptops both ways and they all work without problems.
Since you are using new hardware - it expects the OS to be installed as uefi - so some tweaking options may become disabled. This is my experience with Asus laptops and I'm not sure how well this experience translates to MSI products. If you want to test this out properly - first install UM as legacy boot and then as uefi boot and see if there's any difference in what bios tweak options you can access. After that - setup the best boot option and just leave it.
Regarding accessing the bios - it's easier with uefi - as grub will create a grub menu option called "system setup" - which you can select at startup to enter the bios. On a legacy boot system - this option doesn't show up on the grub menu and to enter the bios you will need to spam (in your case) - the delete key - as soon as you turn on your computer. I hope this helps you out!
Thanks for all the answers 
What @nemo saId is exactly what new mobos require us to do.
1st: Before you start installation, use gparted to create a tiny 100MB partition at the far left side of the disk, and format it FAT32, Once formatted, set the "esp" flag. This is important.
During installation, set that FAT 32partition to boot-efi (it cannot be done from within gparted), and from then all should be jake.
It's M$ forcing us to go though hoops we had not had to go through before, so all these modern mobos default to installing Windoze. 
Thank you @Frederick_Wrigley for explaining what I wrote in a much more simpler & technically more accurate way! My experience from more modern motherboards is that they by default assume that you will be installing Win10 and the bios is configured as such. M$ has clearly paid them for that arrangement! I hope that these new linux hardware manufacturers will finally break that M$ hardware pre-configuration monopoly - and soon! 
/etc/fstab is not a reliable indication. I made a new install of mate 20.04.1 EFI about 6 months ago on a 2 yr old Dell Optiplex of-lease computer.
I have the "grub-efi-amd64-bin" boot loader but in my /etc/fstab there is only
UUID=E2B8-8B25 /boot/efi
which is /dev/sda1
and
#/dev/sda2
UUID=d5853fda-c2a3-40af-bf52-20c59aceab3d /
and gparted shows
/dev/sda1 fat32 /boot/efi
/dev/sda2 ext4 /
The Dell BIOS has "legacy mode" as an option. The system will NOT boot in legacy mode.
John
/etc/fstab is NOT a reliable indication ... you must be kidding!
man fstab
That's exactly what my first sentence said. I guess you just had to be rude.
blkfs and garted certainly are reliable for mapping partitions. I consider gparted to be authoritative.
If Ubuntu is allowed to install EFI mode from a thumb drive without being molested then only two partitions are created, /boot and / . SDA1 and SDA2.
John.