Hello,
Thank you for ypur answer. It's my fault i forgot to say that i use a Lenovo laptop IdeeaPad with AMD Ryzen 5 as CPU and Vega 8 mobile as video card.
My issue is very similar with this one( identical)>
I tried the fix sugested here:
https://www.reddit.com/r/xubuntu/comments/gb9jiu/xubuntu_2004_amdusers_garbled_display_fix/
But the problem still persist.
Any help will be much appreciated
Thank you