There are adaptors to get FD lenses onto RF's, but how will you focus?
I have two Canon RF's, a 1950's leica-like and a G-III QL 17. I really like the tiny G-III.
You can get the fixed-lens G-III for cheap cheap cheap (mine was $35 and works great and is much quieter than an M6). The LTM cameras, rather more $. Pretty good cameras though.