LP_ASUSAny version of Android 10 is downgraded to Android 9 with the same firmware, even for future Android 10.
I haven't tried to downgrade back to 9 with multiple versions of Android 10, that's why I noted it may not be possible with the most current version.
You won't lose access to any of the bands, that is a hardware function that doesn't fluctuate with firmware.
If the only thing you are worried about is the lack of a fingerprint sensor and are otherwise satisfied with Android 10, then I recommend backing up all of your data and performing a factory reset. The upgrade from Android 9 to 10 messed with the fingerprint features for many users, but was easily resolved with a factory reset.