Check out the January 2022 newsletter for the Wunderlinq article. This replaces your garmin with a phone. If you set it up correctly the phone you use does not even need to be directly connected to a cellular service, you can pair it with your regular phone that sits in your pocket.
Wunderlich sells mounting hardware that would allow you the replace your current garmin with the XT. However it would only draw power from the hardware. You cannot control it from the BMW Wonder Wheel.
Kevin Coleman had the same problem with failing Garmins that caused him to go with the Wunderlinq solution.
John Ellis