I wanted to experiment with this: hassio-addons/netalertx/README.md at 46cc46b0d447c1f39624408a937f971c53480715 · alexbelgium/hassio-addons · GitHub
Documentation says it should be available in the add-on store, but it is missing? (yes, I see Admin rights under Settings-People)
You probably have to add the repository - overflow menu top right.