I’ve been helping out with bug triage since Plasma 6 released (I’m not a Plasma developer though, so take whatever I say with a healthy helping of salt). There have been a fair amount of bugs regarding fonts and fractional scaling, and a bunch of them seem to be upstream Qt bugs. So, it’s not just you/your system. There seem to be workarounds for some cases, but unfortunately I can’t say how long it will take for an out-of-the-box fix.