Just a follow-up, I got it to work by forcing SteamVR to take me through room setup, using OVR Advanced Settings, as described here: https://www.reddit.com/r/HPReverb/comments/kvd3m9/comment/gixybqw/?utm_source=sh...
With the SteamVR boundary setup, everything worked great on the G2.
Of course most users will not know to do that. I saw below you mentioned you're looking to support OpenXR, I imagine that will solve the issue for the average G2 user! :)