Partially because it's the latest version but primarily because there's a bug in the current version for QTwebengine.

As detailed at r/qutebrowser - Comment by u/The-Compiler on ”WebGL blacklisted on Guix”, most text gets broken (; I haven't tried other browsers but I've experienced this with Qutebrowser, currently.

It seems the issue was addressed in QT v5.15.7 so an update to, at least, that would, theoretically, solve the problem.