I’m running Dendrite, I expect the best compatibility as this is an official product.

Fair point, I assumed OP meant people of indeterminate identity. Jan Kowalski is indeed the goto placeholder name.

In Poland typically, both officially and informally, one says N. N. (Latin nomen nescio, identity unknown).

Sure, but give us something to work with ;)

Log out and in again, I believe it’s a known issue after upgrade.