Rumors:

Can be crewed, AI or Wireless controlled like a drone.

Aside from obvious bomb mission it will:
Act as Stand off long range AA missile truck were F-22, F-35 and some classified hypersonic and other drones will acquire targets and launch missile from the B-21.

It will perform similar roles for AG and AS, missions.

Can carry SAD drones that are in testing now that will us B-21 as a mother ship. B-21 hangs back while it’s drones move into combat zones to acquire targets for B-21 payloads while B-21 stays in best Stealth zone and configurations.

Also being developed are packages to seek and destroy anti aircraft radars and missile batteries. Some drones will actually be expendable dumb decoys witch can switch into high radar visibility mode to cause air defenses to turn on and give their positions away.

It is fully capable of AA, AG and Bombing missions all on its own too.