I was interested to know how well Leica m lenses can be adapted on Canon EOS R body and was curious about the Canon EOS R sensor glass stack thickness and found the answer here,
https://petapixel.com/2018/10/24/can...de-the-camera/
"The internal low-pass filter and the dust reduction system glass combined had a thickness of about 1.6mm".
Comparing with Sony's A7 series which has a thickness of 1.8mm, we know the first and second generation A7 series cameras suffered the color shift/corner smear issue when adapting wide angle range finder lenses. The third generation has greatly reduced the color shift problem with BSI design, but corner smear of wide angle seems to still remain. So For Canon EOS R, with 1.6mm glass stack thickness and without BSI technology, it might not be a surprise to see the same issue. But thanks for the testing! This is the first report I saw on adapting Leica M lens on Canon EOS R.