So I have both the R5 and the R6. My R5 is a little over a year old just for a reference. On a recent trip I needed to manually override the autofocus on the RF100mm macro and could not do it on the R5. Switching the lens to the R6 let me do it. I know that the canon knowledge base says that the lens is not compatible with electronic full-time manual focus, however it says it shouldn't work for the R6 either. While on the trip there were a few others who had an R5 and it worked for them.
BTW I checked it with a few other lenses - the 14-35 f/4, the 50mm 1.8 STM and the 24-240 f/4.5-7.1 they all work fine on the R6 but not at all on the R5.
Any ideas as to why it will work for some but not others and why it works for my R6 but not the R5?
Thanks in advance
For what this is worth, I have an R5 and an RF 100mm macro, and my manual focus override works fine. I'm using back button focus and FV mode exclusively, in both One Shot and Servo modes, and have it set so that when I turn the manual focus wheel, the EVF magnifies. That works fine also. I have also used this lens on my R without a problem.
I got my R5 in April 2021, not sure how to know manufacture date.
I discovered a setting that you might want to confirm that you have enabled (actually both of these settings--my apologies if they have already been mentioned): (1) Under AF, the #5 tab, Electronic full-time MF should be On (I just discovered that it was disabled on my R) and (2) also under AF, the #4 tab Lens Electronic MF should be On (I have mine set to On + Magnify).
"and have it set so that when I turn the manual focus wheel, the EVF magnifies. That works fine also."
My wife loves that and probably uses it 90% of the time. Drives me crazy when I snatch up her R6 to get a quick shot, LOL! I use manual focus override quite a bit, but I don't use magnify because I have a longer lens.