Huhu, i test it with default config in the README.md and i recognice, that only the first labelName (severity "critical") has an effect. every other severity ( e.g. "info") has no effect (e.g. if i give them an tag).
Thorben Günther referenced this ticket in commit 549793c.
This bug should be fixed now. I have created a new tag for the docker image (
xenrox/ntfy-alertmanager:dev
) which is built from the master branch in case you want that bug fix before the next release.