It is indeed installed, although I'm still wondering what possible impact a security update could have on display artefacts in LibreOffice. And no, I don't have OpenOffice installed.
One thing that came to mind is that the JDK I have installed is a third-party one, Liberica JDK. Didn't cause any issues before LibreOffice 7.5, but could this be the culprit?
I tried: unchecking JRE in advanced options, and messed around with graphics settings. Tried disabling Skia, but it didn't change a thing. Tried software rendering for Skia, didn't change a thing.
When I execute the graphics tests (display options), I get a number of "weird" results.
Example of artefacts I get, when importing a csv file. (Attached, img 1.)
Another one is that when double-clicking in a cell in a spreadsheet, instead of highlighting the content, the content becomes blank (invisible) until I deselect it.
Another one is when opening some odt documents, the text is all over the place. Seems to be particularly happening when there are images inside the document. (Attached, img 2.)