as with every camera you are hardly relying on good lenses. Leica is one example in the higher region.
Regarding the Canon EOS R I went for two more lenses, the Sigma 35, 1.4 and the Zeiss Distagon 21, 2.0
I like the built quality of both lenses as well as the design, and of course the results with the combos.
A new Novoflex Adapter: EOS R on Leica M (Noctilux .95)