What to do if ESPHome shows all nodes as offline

I love the ESPHome dashboard. It shows me all of my notes and whether updates for them are available. However, I was having an issue I had ignored for the longest time: ESPHome was showing all nodes as offline, even though I knew they were online. I was even able to update the notes that were apparently offline.

From what I have read, this issue frequently occurs when running ESPHome in a Docker container and not the Home Assistant add-on. In my case, I experienced it while running ESPHome on my Unraid server.

As it turns out, adding a single environment to the Docker container was all that was needed. If using Docker Compose, the following environment variable has to be added:

environment:
  ESPHOME_DASHBOARD_USE_PING="true"

If, like me, you are using Unraid, you can add the variable using the web interface.