laurentppol's post in [Invalid] - New OrangePi 4 (not B), no image at HDMI was marked as the answer
Ok, found solution:
- restarted from scratch (*.img file -> uSD),
- connected "real HDMI" (some overscan) TV, keyboard,
- gone trough initial config (root passwd, "normal" user),
- configured WiFi (had no wired Eth at my neighbour) using nmtui,
- now SSH works in both directions.
So conclusion is: the problem was / is (still no video on VGA) with cheap HDMI->VGA converter.