It has been very problematic for me, because QT5 does not support Wayland. Under Gnome, it looked blurry. Under Plasma, X11 apps don't get scaled by default, so I used QT_SCALE_FACTOR, but it causes menu mouse position to be wrong. Also, it does not seem to follow the system style, making disabled text illegible.

Thanks @HubKing, that's good info. 😄

Well, I just discovered that it has its own theme/font settings. It had "Follow the desktop style" and "Dark", and I switched to Dark, set the font size to 16, and disabled QT SCALING. I don't like this blue-greenish colour scheme, but I think it's more useable now. Are there more themes than this "Dark"?

Nah, it's just Light and Dark. So far anyway. 😄