users from the US know more about this (I’m EU), but from the threads, T-Mobile and its MVNOs seems to be more flexible and AT&T more restrictive in how they filter devices on their network.
There is some feedback and compatibility lists via New to community-need help finding a mobile carrier - #2 by tcecyk - 4G has a few dimensions: frequencies and VoLTE. But if the frequency ATT offers and the modem is compatible with, then the data block is arbitrary. Voice-over-LTE is a separate issue - see the links.
Was the Murena One sold in the US officially at some point? I remember Murena warning AT&T users in the past.