I researched many different options for cameras and camera adapters, and have currently settled for the SA20 and Canon RF mount adapter from Wraymer. Wraymer is a Japanese company and I’m not sure that they ship overseas. I don’t even see an English version of their website.
The Wraymer SA20 adapter is a mid-range adapter cost-wise, and to be honest, the image quality when using this adapter is not great, but it does enable me to attach my Canon EOS R5 and there is very little of the microscope’s image circle visible in the corners, so with a little bit of cloning I can generally get away without any cropping.
Other options include this kind of dedicated digital cameras from the microscope manufacturers, but I don’t know if the image quality is any better than what I’m getting. Be careful when selecting a digital microscope camera though. There are a few manufactures that are falsely claiming their cameras to be high resolution, like 34MP, when they are actual 3.4MP, which is practically useless for anything other than web use. Currently the highest resolution microscope camera that I’ve seen reasonably priced from a trustworthy manufacturer is the 20MP camera from Swift, but I only see that on Amazon.co.jp, not the US store.