I am tempted by the SL3 suddenly. As I've posted before I have a GFX100 that I use for scanning but it's terrible to use anywhere else. So big. Plus I want a viable body for my Zeiss Biogons. I was thinking of getting the M11. I could scan film with an adapted macro and a visoflex and obviously it's ideal for my M glass.
However recently I've been thinking about the SL3. It's cheaper! Has IBIS, will take a nice AF macro. But how does it compare to the M when using M glass as a casual camera? Is it easy to focus? Will the corners fall apart?
Camera scanning itself is being a bit pushed to the side on my list of needs but it is still a part of my toolbox so...that's why I'm willing to deal with a bayer camera over the nice pixel shifted GFX scans. I know the SL3 does not have multi-shot but it might come.
However I have some suspicions that a future theoretical M12 may have IBIS and thus could have multi-shot? It doesn't even need to boost resolution. 60 is fine...but the RBG capture is wonderful for scanning.
M glass on SL is a pleasure to use, I frequently use SL instead of my M11 with my Nocti 50, 75 and Lux 90 especially. I have not noticed a difference in image quality between SL an M cameras when using M lenses (including the Lux 21). You could argue if e.g. corner sharpness is of the utmost importance, using L lenses will almost always beat M lenses anyhow (and e.g. Sigma 20mm f/1.4 can be had for a modest price), even when those are used for comparison purposes on M11.
The two reasons why I have an M11 and did not upgrade my L mount camera to the SL3 (waiting for SL4 - years away - tbd): 1. Leica's reliability issues (!!!) in combination with a month-long, ultra expensive repair process (!!!); 2. Leica's choice to build the digital part of the SL3 around a slow SOC (Maestro) that will prevent them from significantly improving aspects like autofocus performance via firmware (e.g., Panasonic S1R II is running circles around SL3, but does not perform as well with M glass).
