Sorry for resurrecting this thread from the dead but from what I can recall of my VR experience.
OpenVR/SteamVR has gotten a lot better but some games like
VRChat are still extremely jank. I know
NO-VR HL:A is possible on the steam deck. It should be possible according to
ProtonDB, you might need to put in some tweaks like....
-novid -safe_mode
or
-novid -safe_mode +hlvr_continuous_normal_speed 180 +hlvr_continuous_combat_speed 180
Used Vive's are good but if you are able to splurge get used index controllers if you can too. They are genuinely a game changer compared to the awful OG Vive controllers.
If you have anymore questions or want me to test HL:A VR on linux just shoot me an email.