I’ve had problems with Libre Office Writer display on my 2017 iMac (Retina 4K 21.5") for several years. The only useable version I’ve found is 220.127.116.11. But it still has odd artifacts in the display:
I keep trying new versions when they come out, but the garbage on the display is never fixed.
Here’s what happens with 18.104.22.168
No amount of tweaking the settings can fix this. Sometimes, scrolling will cause a window redraw which fixes it for a while, but the screen garbage always comes back.
Both of the above screenshots are of the same document which was created on an MBA running version 22.214.171.124. (That version works for my wife on her 2015 MBA running Catalina, but wouldn’t work for me on my 2017 iMac. Based on my bad experience with recent versions, my wife has decided not to upgrade.)
For me, the only recent useable version is 126.96.36.199. That’s the only solution I"ve found.