Interesting, in that case I may just go with the older magisk you are using and see if that works. I just tried the combo that fritz used and it isnt working either. The Magisk manager (8.0.7) is not even seeing that I installed magisk 21.4 so I think I will scrap it and flash back to the original Modest rom 11 and then simply see if I can update magisk from there. Do you know by chance if your current setup is passing safety net?I'm on Magisk 20.1. Not hidden. adb is working fine, Bank of America app also working.
Also, were you able to get the T-Mobile VoLTE working?