I realized that qtcreator started using 100% cpu, without exception. Yet, the UI works and I can edit stuff. On some files, editing can be sluggish though ( a multi-second wait until I can select text can happen on specific files), but I'm not sure whether these issues are related as I experienced this sluggisness since quite a while.

The only idea for debugging this was to use perf top, so I'm attaching a screenshot to it. Note, I have no other app using qt5 on this system, so clearly these events must come from qt-creator application.

If you need any more info, just let me know