Yes i did use the Fast Network Camera option and _that_ works.
However, I have one simple reason to try without the Fast Network Camera option and that is the "Automatic Brightness" that is available when the camera on the PI is configured without the Fast Network Camera option but not available otherwise.
It appears after a few days of running the PI this way the Automatic Brightness option does a rather good job during evening and night etc...
And yes I did try the URL with and without port number.
When configuring a network camera the port number must be included in the URL or motioneye shows the message "not a supported network camera"
When configuring a Remote Motioneye Camera the port number must NOT be includes in the URL as you mentioned before.
Switching to Fast Network Camera is indeed my option to get this system up and running at the cost of not having automatic brightness adjustment.
I recall reading a few articles (a few year ago) about re-configuring motion (not motioneye BTW) for day or night operation based on day of year, time, longitude, latitude and that kind of stuff. that appeared to my as rather complex stuff, would like to avoid that when possible :-)