I recently got a Canon R50 with the Tamron 18-400mm F/3.5-6.3 Di II VC HLD (with EF-EOS R adapter). Quickly I loaded a RAW file into Darktable to see if it recognizes everything, unfortunately this appears not to be the case.
If I understood correctly, by sending a RAW file I can help you recognize my camera. If that is correct I would like to hear where I can send it, otherwise I would like to hear about it.
With recognizing my lens, Tamron customer service told me that if it is on Lensfun it should also be recognized. On Lensfus my lens can be found and it says it is fully recognized. I did read somewhere that when you use an adapter, you have to add it manually. I did not understand how and where to do that and would like to hear how this works exactly.
With that said darktable opens R50 raw files, but with wrong color matrix and wrong crop.
144px crop from left side, 40px crop top and 0px crop right seem to be better than 168px, 52px and 24px. You will see the full image if you go to the module raw black/white point and in the hamburger menu click passthrough.
About Lensfun then. No one has added your camera there. It is really a simple task. You need to create the following: