If you wrote without KDE dependencies and your distro did include the correct Qt version, there's no problems at all (apart from edge-case bugs). But KDE3 to KD

If you wrote without KDE dependencies and your distro did include the correct Qt version, there's no problems at all (apart from edge-case bugs). But KDE3 to KDE4 and KDE4 to KDE5 (Plasma) was associated with a whole change, similar to Mozilla's Firefox's "Daylight", "Quantum", and "Australis" and web extensions, and associated behavioural relearings.