@autistikai commander, owner, sovereign

@autistikai Mx. , Mxtress, and Mxter are good options I think

Also different descriptive terms depending on the scenario can work I think, like owner, my liege, your majesty, whatever works in the moment.

Or just Dom too, though that's sometimes seen as gendered. But at least when spoken out loud there's not much of a pronunciation difference between Dom and Domme