I’ve heard people trying to replicate Alec Guinness on YouTube. It never sounds 100% right.
I think the problem with a lot of people’s clones is that they use audio with background noise or poor mic quality. Either that, or they don’t use enough samples. Unfortunately, older actors have voices that fall under all three of these categories.
The best replications by far use ebook readings, podcast samples, or video game voice lines ripped from the game files.