I have had similar issues with my Mavic Pro Carbon USTs.
I tried to mount GP 5000 TL but there was absolutely no chance to get these on the rim. Tried all tricks that I could find on the internet as these rims seem to be known for complications.
Now I am running Schwalbe Pro One TLE, which were also close to not mountable, but with all the skills and tools that i acquired over time, I managed to get them on. However, I will never ever be able to get these off and back on at the side of the road with two levers. Im just praying that i dont get a puncture.
Does anybody know if its easier to mount non tubeless tyres onto the Mavics. That’s my secret hope. I am not a fan of tubeless anyway. It let me down twice already.