This QuakeVR port is actually really cool, VR feature wise almost comparable to HL:Alyx and definitely surpassing a lot of commercial VR titles:

Source-code can be found here:
https://github.com/SuperV1234/quakevr

Features (as of v.0.0.6):

Smooth locomotion
Teleportation
Fully room-scale (including jumping)
Hand tracking (including full finger tracking)
Weapon models with hands and ironsights
VR interactions (melee, headbutts, pick up items, press buttons)
Steam VR Input API support (can rebind inputs in Steam VR settings)
Brand new particle system (smoke, blood, lightning effects, and more)
Haptic feedback (weapons, melee, damage, interactions with items)
Two-handed weapon aiming (with virtual stock support)
Weapon weight simulation
Positional damage (headshots, leg shots)
Weapon holster system (hip and shoulders, fully customizable)
Weapon throwing & force grabbing
Multiplayer support (also with bots)

This could probably be used to make a stand alone FOSS game that would turn some heads even from people that otherwise shun them completely...

I think Linux support is untested, but should in theory also work (But it might be easier to just run through Proton like most VR games on Linux). Edit: It works with Proton, but I am having issues with my Vive Wand controllers... seems more geared towards those Index controllers :(

For completeness sake: there is also a different Darkplaces engine port to the Occulus Quest by DrBeef that also sounds quite cool.