/etc/exports
/my_share 192.168.122.0/24(rw,sync,insecure,no_subtree_check,crossmnt,fsid=0)
sudo exportfs -arv
sudo systemctl enable --now nfsv4-server.service
I tried this instead of only rw and sync but no change.
I made the change to home and selected it for the local network, but no change. My home zone config:
I googled a few hours about the plasma-firewall and firewalld, there seems to be a conflict, but also not really a solution and also not really a documentation about plasma-firewall or I have just missed it.