Only reason, may be moot now, to use the .deb/.rpm/whatever is for VR as it is a little picky. Same as you I use flatpak for everything else where possible, lutris/bottles/emulators, just remember to also install flatseal to edit permissions (I store some stuff on an external drive, like downloads/videos and VR steam games I'm not playing but will and don't want to wait an hour or more to get, so had to add the path)

Oh! just remembered that somehow protonGE was installed (lutris or bottles? maybe fixing stuff while drunk) and steam picked it up and now plays videos in UE games, maybe a second reason? I'm wondering how that works but am not going to look a gift horse in the mouth, those teeth are scary.

Using Kubuntu 24.04, streaming VR games live. Setup is a snap (don't use snap except where Kubuntu already did and even then I switched to flatpak FireFox as snap FF started being... difficult