Noo please don’t Ubuntu. Just plain debian or mint debian instead for the closest thing without canonical. Ubuntu is based on debian and all the actual reasons to use it over debian ended probably like a decade or so ago.

I don’t think there are many distro specific proton issues, if they exist at all. I’ve switched from arch to tumbleweed to bazzite(ublue/fedora based) and the only issues were unrelated to gaming. Proton would work on a toaster if it had a display and a vulkan compatible GPU.