These are mainly Scifi and Fantasy booktubers for Adults:

Petrik Leo (mostly epic stuff)

Library of Allenxandria (also likes historical and military fantasy and ancient greek / rome)

Mike's Book Reviews (also likes manga and Steven King)

Emily Fox (a little bit of every genre)

Liene's Library (more diverse genre as well, very well spoken and has excellent in depth reviews)

Elliot Brooks (super wholesome, will sometimes do YA fantasy too but less so)