I am the author PINN, my fork of NOOBS that allows easy installation of many OSes (currently over 60 different OS variants) on the Raspberry Pi.
(See https://www.raspberrypi.org/forums/viewtopic.php?f=63&t=142574 and https://github.com/procount/pinn/blob/master/README_PINN.md)
It has many more features than NOOBS such as: reinstallation/replacement of individual OSes, backup and restore of OSes, disk checking and recovery features etc. that make it more of an OS administration tool.
I previously made UbuntuMate 16.04 available for use with PINN, and I have now just completed adapting 18.04.2 beta1. This will be soon be made available in the next version of PINN under the testing category until it comes out of beta, when it will revert to the General category.
@Wimpy - The main reason ubuntuMate 18.04 requires the next version of PINN is the way this version handles its partitions, relying on the Label names of the partitions for reference. PINN is a multi-OS installer and boot manager, and its recent versions allow multiple copies of the same OS to be installed using its ProjectSpaces features. However, because of 18.04's use of partition labels, I have had to exclude 18.04 from being installed multiple times as I imagine the wrong partitions will end up being linked to, or shared between the 2 instances.
I imagine this use of labels is because of the extensive configuration that UbunutuMate does at startup and using labels makes it easy to find the other partitions, assuming they are unique. But I don't remember this being a problem with 16.04. Is there any specific reason for this change?
Due to the relocation of the OS partitions in a multi-boot environment, PINN updates a few files on installation (like cmdline.txt and etc/fstab). Typically for an SD card installation it will use the /dev/mmcblk0p6 notation and for installation to a USB device it will use the PARTUUID=123456-06 notation. For 18.04, PINN needs to maintain its use of label references.
I don't know if there is an easy adaption for this, or whether it is indeed necessary, since I imagine users who install UbuntuMate will only install one version for use as their main OS, but I'm just highlighting the issue.
I notice uboot.bin is present on the initial image, and some other uboot files get created after initial configuration. Are these actually used in the RPi environment, or are they just hangovers from the configuration process being suitable for many other targets?