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 just launch steam big picture through moonlight and use the host client’s steam configuration you’d just be configuring an emulated Xbox controller. (which might be fine for your use case) you’d lose out on all the steam deck specific bells and whistles. No grip buttons or touch pads. If you use moondeck you keep all of the steam decks funtionaitly.