This video is old way.

Better: use AR Core for built-in 6DOF head tracking, Touch Pro controllers auto-synced / calibrated via shared markers from a Quest 2.

Then SteamVR -> to phone using CloudXR, and Monado (OpenXR) on the phone side for late warp.

youtube.com/watch?v=cljOJC…

Here's Monado running on a mobile phone (already a couple years old):

What's best about this solution is that CloudXR 4.0 (whenever it's released, it's late now), can actually support all the data on the PC / game side through OpenXR that you could possibly want. Hand / eye tracking? Sure, forward it and patch it in.

It's open source, just do it.