Much appreciated! Yours and pnbruckner's work bought us some time.
I checked out that branch earlier today and was considering an attempt to implement it but at this point, I think it's time to move on. I'm pretty sure the issues are beyond auth. Access tokens were working with some endpoints and not others.
Some pretty cool work has already been done to get OwnTracks to Hubitat. [RELEASE] OwnTracks for Hubitat Presence Detection