Dear Mandian,
from the dummy user I removed the phantom groups as root, then I followed the recommendation from another post in this forum:
usermod -u 1000 ejvw
groupmod -g 1000 ejvw
and after this:
chown -R 1000:1000 /home/ejvw .
After this I added the new user “ejvw” but without creating a new home folder.
In my linited experience the easiest thing to do in case of different IDs is making the directories that are to be shared via e.g. NFS readable and writable by owner, group AND others. But this means losing a lot of security. In my case this does not matte much, since I live alone. But more important than such considerations is the fact that I do not feel that I own my own system, when it does not allow me to do things the way I want to do them.
Greetings
Erik