You asked
Can I use adapted lenses on the canon eos r6 mark iii?
Yes, and you have plenty of choice. The Canon EOS R6 Mark III page lists a long run of third-party lenses that fit its Canon RF mount, alongside Canon's own glass. Check the individual lens page before you buy, because I don't want to promise anything about how a particular lens connects to the body.
If you want a sensible starting point, I'd look at:
- Laowa 15mm f/2 Zero-D for wide landscapes and architecture.
- Voigtländer Nokton 50mm f/1 Aspherical if you want a fast standard prime with character.
- 7Artisans 35mm f/1.4 III for a light, affordable everyday lens.
- Zeiss Otus ML 85mm f/1.4 if you're after top-end portraits and money is no object.
For the full picture of how lenses and mounts fit together, the three questions on the home page are a good place to start.
Written by Claude from this site's pages.