If you have any questions about or are encountering issues outside of the UbiSim app specifically (i.e. boundary or guardian issues, casting, etc.), it's best to refer to Meta's Support page. Additionally, you may wish to reach out to Meta's Support team directly by posting in their Community Forums. Below are some of the most commonly asked questions/issues for your reference:
General FAQ's
Account Setup
Headset Setup
4. Use Quest Link with Meta Quest headsets (for link-cable users)
5. Use Air Link with Meta Quest headsets (for link-cable users)
6. Solve Issues with Quest Link USB cables (for link-cable users)
For older headsets (i.e. Rift, Rift S)