Hi, i have exact same problem as above poster on RPI4 LibreELEC 9.2.1.
I get a white line above with white snowy artifacts coming down from the top, same as images from above poster.
Its happens when i use the plex addon or just kodi.
It fixes the issue when i uncheck 4K capable and leave the others checked such as HEVC and direct play etc.
I'm guessing unchecking 4K reduces quality to 1080p though.
Thanks.