I have a 2015 Ford Escape. My S21 was working in the car just fine until today. It will not sync no matter what I try. I seriously doubt it is the car as so many other folks are experiencing the same problem, all with the same phone and different vehicles. In fact I just had a software update to my phone on April 9, 2021.
Unfortunately the problem returned. Weird because i went 40 minutes without skips before i posted. Went out this morning and it was worse than before. I think i might try unpairing and then pairing again without allowing calls or messaging.
Setting AVRCP to 1.4 fixed it for me, otherwise I couldn't connect to UConnect on a 2019 Challenger. For some reason AVCRP was set to 1.6. It could connect to other cars just not Mopars.
Most manufacturers will leave it stock like from Google but Samsung adds their Scalable codec and tries to promote their Buds with it, by cutting support to other Bluetooth devices.
I recommend to connect the phone with USB C or Android auto or line in.
Don't expect much from Samsung.
Android Auto is broken on the S21 Ultra. I tried yesterday on my 2018 Audi Q7 and it wont even recognize the device. it only charges it but wont launch android auto. even the pixel 2xl i have connects today with no issues. i wonder if the default codec for Bluetooth can be changed via developer options.
Android Auto and Bluetooth work just fine with my Ram 2020 Uconnect system but AA would not be recognized by my Wife's 2019 Kia, Bluetooth was fine though.
Galaxy S21 Ultra 512g(VZW), Galaxy Book (original, VZW), Tab S4, Galaxy Watch3 (VZW)