Comment 12 for bug 1862467

You're not wrong that there's a bug with the sizes of certain controls when you just change the font size or DPI. However this is because these controls are meant to be scaled using the Qt scaling system (which gets invoked by changing the global scale in the KScreen KCM) rather than scaling perfectly with the font size. What you're trying to do is bypass that system and set an *effective* scale factor using a totally different method to work around a bug in GTK apps, which is not something we explicitly support.

That said, GTK apps should scale perfectly with integer scale factors (e.g. 2x) set from the kscreen KCM. They do for me with a 200% scale factor in Plasma 5.20. What version of Plasma are you using?