I am currently contributing to Prometheus Alertmanager. Most recently I added support for Unicode (UTF-8) as part of a larger effort to adopt OpenTelemetry (OTel) in Prometheus. I wrote a parser in Go, that replaces the existing regular expression parser, to enable parsing labels and label matchers containing Unicode. It eliminates all parsing ambiguities found in the existing parser while maximizing backwards compatibility.
I have also contributed a number of other features, bug fixes, triaged issues and reviewed pull requests from the community. I have built up a large amount of domain knowledge in Alertmanager and have written a number of blog posts on it.
You can find all my contributions here.