Hi all, I'm new to Ubuntu MATE but not Linux; I've been using it as my primary OS for a bit over 4 years now. I'm having an interesting issue with UM that I've never had before.
My PC is set up with 3 operating systems on separate SSDs: Windows 10, openSUSE Tumbleweed, and recently installed Ubuntu MATE. While all the data and whatnot is on separate disks, the bootloaders all seem to be on the same SSD, the one where openSUSE is installed. Not sure how that happened, but in the process of several distro hopping adventures and having to reinstall Windows, that's what I've got. It's worked fine so far - I set openSUSE as the first boot option in BIOS, and select my OS each time I reboot via grub.
However, installing Ubuntu MATE has screwed with my setup somehow. Every time I boot into UM, it seems to hijack my boot settings, and upon the next reboot my PC boots straight to UM instead of giving me the option. Not only that, the other bootloaders disappear from my BIOS settings completely. The only way I'm able to get it back is hit F11 and manually select a different SSD (which oddly doesn't even have an OS on it, I just use it for storage), and then when it tells me there was no OS found, I reboot and magically have my bootloaders selectable again from BIOS and the F11 menu.
I've had the full spectrum of Linux distros on the drive that UM is on now, including standard Ubuntu and Ubuntu Budgie, various other Ubuntu and Arch distros, Fedora, etc. I've had openSUSE installed for a little over 2 years, and my Windows install was probably done around the same time as openSUSE.
Any help with this would be greatly appreciated - it's quite the hassle to reboot multiple times when I want to switch from UM to something else, and more importantly I'm afraid that sooner or later something will get corrupted if I keep doing this process. Let me know what kind of information I can provide for troubleshooting.