Yes, done, it works!
First -not knowing the diff- installed gtk; then -being KDE- removed it and downloaded / installed qt.
The latter does not give me hints (words) over buttons, but that's OK. Amazingly, Save => Video gives me options for mp4, or avi and other formats.
The results seem to be fine, for basic work like trimming. No chapters, though. Thx, ppl, rgds