i went back to the 2023.1.2 yesterday and the same problem are back on that version to!! I feel stupid because my 2023.1.2 was perfectly working and i don' know why i updated to the 2023.2 because now i'm stuck between 2 versions that i can't work with like i should be.
And just like you i've tried everything on your list, so now i don't really now what to do, maybe check your Manage 3D Settings didn't change anything for me but we never know.
And i've also noticed that when i use twinmotion the GPU of my NVIDIA GeForce RTX 4080 is always at 97% - 100% on my task Manager, but it's way lower on my laptop (i pretty sure it shouldn't be that high).
