TrackIR has been fixed in the upcoming optional “public beta” that is to be released tomorrow. I’m using it now and it’s back to normal.
Hopefully, and this is purely based on 1. the version number 1.21.17.0 and 2. the wording in the insiders hub “Sim Update VII Update preview” that this is indeed an SU7 patch as an optional preview to get a large feedback base before a full release to fix this an other pressing issues.