Connect the Steam Deck to a compatible dock and you can quite easily use it as a desktop. At the end of the day, it’s still an x64 based PC that’s just handheld.

Linux user here running FF, no real dealbreaker issues at my end.

I’ve got plenty of old software here under Linux that still runs fine to this day across a number of PC’s and even a Raspberry Pi that I use as a backup desktop. I honestly can’t see backwards compatibility being any more of an issue than it is under Windows - There’s a number of accounting packages released under Windows 7 that won’t run under Windows 10, the latest version of most popular browsers won’t run under Windows 7. Likewise, the latest version of MS Office 365 won’t run under Windows 8.

My overview transition is seamless running X11.

RTX has worked under Linux both natively and via and Wine/Proton/DXVK/VKD3D for quite some time now.