That would be first Doctor of colour.
- Jo!Doc is from the future but for some reason doesn’t remember being Jodie!Doc.
- Jo!Doc is from the past (pre-Hartnell!Doc? between Troughton!Doc and Pertwee!Doc?), but for some reason Jodie!Doc doesn’t remember being her.
- Jo!Doc is from an alternate timeline.
- Jo!Doc is a fake.
Chris Chibnall has explicitly denied the last of these: but remember that, like the Doctor, showrunners lie.