Full specs in first comment.
So first of all, this is not a "Linux sucks" rant, I want to make that clear. I've been using Linux for over 10 years now. Started with Ubuntu, moved to Arch, now on openSUSE Tumbleweed on both my desktop and laptop. I'm a software dev by trade and sysadmin by hobby.
But why in the shit can Valve not get Remote Play on Linux in a useable state? Let me lay out my evening yesterday.
I took my car to the shop for an appointment that I knew was going to last 4+ hours, so I took my Steam Deck. I finished up Spider-Man 1 and moved on to Miles Morales. All of this was flawless (as was playing most of Spider-Man 1 on Tumbleweed, btw).
I got home and decided I wanted to remote play MM from my desktop to the Steam Deck in the living room. All wired, no wifi. The reason for this is that I want to use the power of my desktop to get high quality graphics, as opposed to the medium settings at 30 FPS I get with the Steam Deck. Note that I've done this with some games before, notably Persona 5 Royal, but it's been a year or so.
I launched MM for the first time on the desktop after selecting Proton-GE 8.0-6 (since that's what worked with SM1). Immediately, I was greeted with a warning that my drivers may be out of date. They aren't, but whatever, I clicked okay and the game launched fine. Cool, that's fine, I figured I'd just launch the game on desktop before I go back to the living room and connect with Remote Play. I messed around a bit to make sure it would play okay, set my graphics options, etc., it worked perfectly.
I went back to the Deck and clicked Remote Play. It attempted to connect, but threw me back to the library screen. Weird, but okay. I re-launched Steam on my desktop from terminal, so I could check the logs the next time. Tried to connect again, and it worked. Weird... but okay. Except after loading a save, I was again thrown back to my library screen, with no option to re-connect. I checked my desktop, and the entire game had crashed. Weird. So I rebooted my machine and Deck and tried again. Same thing.
Okay, fine, I figured, you know what, this is one of the things I have a Windows VM with PCIe passthrough for. So I booted the VM, booted MM, set graphics options, everything was great, cool. Went back to the Deck, and tried to connect. Again, it attempted for a second and then sent me right back to the library. That's wild. So I rebooted the VM and the Deck and tried again. Got connected and loaded the game, it didn't crash, alright, cool, we're in.
Next, I started running into issues where I was getting random inputs on menus. Specifically only menus. Weird, but as long as my save doesn't get deleted, no big deal, I guess. So I played for a few minutes, then noticed the frame rate was super choppy, even though the FPS overlay from the host was reporting 100+ FPS. The Deck overlay had errored out and was reporting 3000+ FPS, which obviously isn't right. This is actually a problem I'd run into with P5R before, so I knew the fix was to go into quick battery settings and toggle the per-game profile. This fixed it, but only for a few minutes at a time. I don't remember P5R having this issue so frequently, and it's also a much bigger nuisance in a game that's not turn-based.
I eventually gave up and just moved back to my desktop (Tumbleweed) to continue playing, where everything worked perfectly (minus the outdated driver warning). Needless to say, it was a very frustrating experience for me, and that's not a good thing. I couldn't imagine ever taking someone who's never used Linux and dumping them into that situation. I really hope Valve works on stuff like this.
What hypervisor are you using for windows in Tumbleweed for GPU pass though?
QEMU/KVM with virt-manager as my front end.
Thanks for that kind sir!