Remote play is already semi-broken on stable. In the sense that the video renders super dark unless you disable hardware decoding.
https://github.com/ValveSoftware/SteamOS/issues/1246
The beta and preview channels are even worse. The remote play session will just never load at all.
https://steamcommunity.com/app/1675200/discussions/1/3757725080156008363/?l=czech
https://github.com/ValveSoftware/steam-for-linux/issues/10461
It seems like this is slipping through the cracks. I’m making this post to raise some awareness on the issue. Not sure what we can really do though.
Edit: God damn it valve.
If you set up the moondeck decky plugin you can use your configurations without any hassle.