I was able to run 3 mongod instances, and add the m103-admin to the primary node. But after connecting to the primary with the following command
mongo --host "m103-repl/localhost:27001" -u "m103-admin" -p "m103-pass" --authenticationDatabase "admin"
After that I get an issue with running
rs.add(). When I run it it throws the following error
2020-10-03T12:01:11.740+0000 E QUERY [js] TypeError: cfg is undefined :