I have been updating with the Nightly Test builds (currently LibreELEC-RPi4.arm-9.80-nightly-20210205-3420901) and notice gradual improvements, such as fixed screen wrapping. I appreciate the effort devs are putting in the get the Pi4 working properly.
So that being said, there is one issue that has been present since 4K was enabled several weeks ago. When the resolution is set to the default 4K 3840 x 1920 @30Hz screen blanking occurs. I thought this was on 4K videos only but the screen blanks occasionally on any resolution video playing and also while playing music files ie MP3s. I am using an effects plugin while playing music. When I set the resolution back to 1920x1080P @60Hz no blanking occurs. I'm OK staying with 1080p but it would be nice to have 4K working.