Just install antfix.zip
on your recovery.
Copy libbt-vendor.so
file to /system/vendor/lib64/
.
Tested Xiaomi Mi5 (gemini)
adb push libbt-vendor.so /sdcard/
adb shell
su
mount -o rw,remount /system
cp /sdcard/libbt-vendor.so /system/vendor/lib64/
chmod +r /system/vendor/lib64/libbt-vendor.so
mount -o ro,remount /system
If you install library, ANT Tester will print right Built-in firmware version.
If you want actual patch, please check this review request.
I don't use official firmware, but it wouldn't work samely as your case.
at least, ANT+ of MI5 works well on lineageos 18.1(android 11) without any extra job.
it's just highly related their build configure.
so, firmware maker just do building with right configuration, ACT+ will be works very well.