Thanks for the feedback Quade777
Actually I got the same error when I tried to bump kernel in my 20.04 installation to 5.9 - evdi seems to be not compatible with this version of the kernel. On the other hand it worked with unofficial 5.8 I also installed - the screen tearing was still present tho...
Changes for 5.9 are still on dev:
https://github.com/DisplayLink/evdi/...4c633c090f7ddc
I think (or rather, hope) that your problem is caused my some minor difference between pure 5.8 and ubuntu's "production 5.8" kernels and can be easily hotfixed
Btw. just for the reference, are you on intel or amd?