The setup script cannot be used on a NAS, you have to use the manual method. But since you are able to run commands on the NAS, let me lead you trough it.
First step is to stop and remove the old Extension Manager:
docker stop roon-extension-manager
docker rm roon-extension-manager
Next we have to collect some system information, write down the number that is outputted by this command:
stat -c '%g' /var/run/docker.sock
And find the name for the timezone you are in, possible values can be found in the TZ column of this list.
The last step is to create the container for the Extension manager. Replace the <docker-gid> part with the number you wrote down previously and replace the <timezone> part with the name of the timezone (make sure that you also remove the < > characters):
docker run -d --network host --restart unless-stopped --name roon-extension-manager --group-add <docker-gid> -v rem_data:/home/node/.rem/ -v /var/run/docker.sock:/var/run/docker.sock -e "TZ=<timezone>" --log-driver journald theappgineer/roon-extension-manager:v1.x-standalone
If all went well you should now find the 1.0.0 Extension Manager in Roon.