Although it seems like a long shot, Android 11 works fine on the Xiaomi Mi A1. The POSP ROM might not be perfect but looks very good and seems stable enough for daily use. The version that I installed on my handset comes with the January 5 security patch, and it also seems to support Qualcomm aptX.
https://www.notebookcheck.net/Android-11-on-the-Xiaomi-Mi-A1-via-POSP-Not-perfect-but-good-enough.515484.0.html