When running Dia under Fedora 33 in a GNOME 3.38.1 Wayland session and 4K screen resolution and a scale factor of 200%, it opens up with very small and barely readable screen estate.
This issue is a stub to track HiDPI support.
Common workarounds like prepending
QT_SCALE_FACTOR show no effect.
As a user of a contemporary linux environment, I would like to run Dia in HiDPI mode, in order to have it display a readable and thus usable user interface.