They’ve recast a few; specifically, Tim Treloar as the Third Doctor, Graeme Garden and Rufus Hound as the Monk (May be new incarnations), Jon Culshaw as Kamelion (default robot form, I’d assume) and Juliet Landau as a new Romana. David Bradley does an alternate Fist Doctor, but otherwise the First and Second Doctors are recreated by other original cast members. There’s a new Rani as well.
In the Sixth Doctor’s final adventure, you’re thinking of the Valeyard, who Michael Jayson return to portray.
Overall, only two definite recasts that I can think of, and the rest are Time Lords, so they could be regenerations.
Edit- BF also created their own incarnation of the Master between Roberts and Jacobi, but that doesn’t specifically fall into your question.