I tried to create a “service account” with a PAT to be used for external scripts. Using a delimited file source and specifying a uid of spadmin appeared to work. However when you try to view that identity you get a blank page and once it is created it cannot be deleted without removing it from the source file. I was able to invite the user, but couldn’t set a password nor reset a password even though it appeared like it should work.
This seems like some buggy behavior for what is perhaps a reserved identity that isn’t obvious.