QA needs to be paid. Largely nobody is doing QA as a passion.
As for UX, if these are the same wizards working around Windows/mobile/web, then please keep them away by all means necessary.
As for ux, open source is not a job. Ux folks are told my product managers to enshitify things on daily basis.
I imagine open source can provide a safe haven form all that and let people run wild beautiful ux and uis. Imagine someone working on the ux of a linux distro aimed at making onboarding of casual users easier.
Imagine a group of people putting together a nice set of guidelines for ui and ux similar to how apple has guidelines.
I think these are two areas where linux (distros) have gaps.
As for beautiful UIs QT has made a step forward with the Qt Quick and Qt Designer which allow a more UX workflow for the UI as opposed to old school dialog/form design.