5 Timey Wimey Clues To Where Ruth Fits In Doctor Who Canon
1. Ruth Worked For The Time Lords And So Did The Second Doctor
One of the biggest giveaways to when in the Doctor Who timeline Ruth is from is her past. We know that she previously worked directly for the Time Lords before deciding that she didn't like it and running away.
This fact plays into a time period many fans and expanded universe writers have speculated about for decades. Season 6-B, the period depicted in The Five Doctors and The Two Doctors respectively in which the Second Doctor is clearly at large following the events of his trial.
In The Five Doctors he uncharacteristically worries about breaking certain rules and we see unambiguously that Jamie and Zoe have already been sent away by the Time Lords. By The Two Doctors not only has this version of the Second Doctor visibly aged but we also see that he's gone back and picked up an older Jamie. Most importantly in this final appearance we see him taking orders and running missions from the Time Lords. This very much falls in line with the type of work that Ruth escaped from.
This leads to a conclusion about the Timeless Child. It is not a person at all but a Time Lord spy organization which recruits captured renegades as assets and returns them to their timelines with no memory of their work. Taking the first two episodes of the season into account it makes a kind of sense that the main arc is still all about spies.