If you go to https://factorio.com/profile while logged in does it show your deadname? You should be able to change it there.

If you've already changed it it's possible the old name is stored in the save and won't change until updated. I know there's been a few threads about this, and I could ...

As title describes. When hovering over an entity, the Last User shows my steam username (the unchangeable one) instead of the LAN player name (the one that's synced with the steam account name).

This is particularly important to me as my steam username is my deadname, and I cannot change it ...