I must admit I didn't even considered this would need spoilers.

Tennant is back as the 14th Doctor before handing the baton to Gatwa. It was a cunning move from RTD.

I'd also recommend persisting with the Capaldi run - it had a rocky start (I think a lot of writers of the early episodes didn't know who the new Doctor was so they were writing generically, and pretty poorly in some cases) but it does hit it's stride and there's some of the best episodes of nu-Who in the later part of his run. Skip the Chibbers era.