Port in use error usually means that Node-RED is already running, which is what you have found.. You just need to stop the version that is running before starting another.
Good,
Two services were apparently running here:
node-red.service
nodered.service
I quit the service:
node-red.service
and disabled:
sudo systemctl disable node-red.service
After restarting, the following error appeared:
Some settings like mqtt and telegram came with their credentials blank.
I filled it again and it worked again, I'm following up.
