UltraVNC

Aye, there was a "missing configuration".

I forgot that the default VNC screen sharing password can have, at most, 8 characters.

The one I used had 10, so 2 characters were truncated from the end...

Once I changed the screen sharing password to one with just 7 characters, everything worked like a ...

Forgive me if this is a silly question, but I've been searching in the forums for a similar question, and the best (and most recent) one I've found was here . There are some interesting considerations back from 2006 or so, but they really don't apply to my case any longer...

So, my question is ...

... just to clarify, what VNC viewer are you using on the Mac?

1. Screen Sharing.app (native macOS VNC viewer)
2. UltraVNC running as a Java application
3. Something else

I'm just curious, I've been trying to connect with Screen Sharing and TigerVNC, without any success whatsoever...