Before CalyxOS took a hiatus, their OS on my Pixel 4a5G would connect to my 2013 Hyundai Elantra's bluetooth in the car. Then after the hiatus when we had to reinstall the OS, it would not connect, and I have changed settings; A2DP on/off, AVRCP versions, Map versions, and it still would not work. Well I just received a new Pixel 9a, and out of the box running Google android 16, it connected immediately. Flashed CalyxOS on it, same, can't connect.
AI thinks CalyxOS has maybe left out some of the old legacy Google Vendor blobs and that one of those deleted Google blobs contains the exact legacy security handshake module required to pass a primitive 0000 Bluetooth PIN. Without it, the de-Googled operating system simply lacks the math to talk to a 13-year-old Hyundai radio chip. Has anyone else come across this?