We are 1 step further.
Apache was using php7.2, even though no 7.2 module was enabled. After uninstalling every existing php7.2 Ubuntu package and rebooting the server (apache restart didn’t work), apache is now using php7.4.
Now we can start nagvis and use “automap” and 2 of 6 custom maps. The other maps throw an error that disappears after half a second and then only a white screen is shown. I catched a screenshot of the error message:
