Two ways to retcon the Timeless Child
1. As the Master was the one telling the story via the Matrix, it's very likely that the Master was channelling Chibnall and LYING to the Doctor about her origin by manipulating it, so it would be easy to debunk that in a future episode. The Master has manipulated the Matrix before.
2. The alien being known as the Doctor now was most likely going by his/her real name beforehand and not using the moniker Doctor yet, not until he/she regenerated into William Hartnell and made his momentous decision to flee Gallifreyan society in a Type 40 TARDIS, so only THEN did he give himself the title of Doctor. The "black Doctor" could be before William Hartnell, but refers to "Doctor" so Whittaker's Doctor knows she is technically her.
Any problems with these two?