Missing Information to correctly start tor relay
When new users want to support the tor network and are planning to build a tor relay, they'll face a Major issue which newer users may not stumble across and therefore stop with the task and never create a relay for the network.
The "Address" option should be added in the Guide's step 2, where the torrc config file is shown.
Without the Address option the service listens on IP 0.0.0.0, which is, as you may agree, not working.
After adding the Address option and inserting the public IP (or DNS name), the tor service can successfully introduce itself to network.