curl | sh
, the website is full of marketing
texts and broken markup with little focus on technical details, only
minimal mail integration. Quite bloated, includes a CI service. Not
sure why, but seems to be pretty popular at the time of writing (the
end of 2018).
There are various attempts to integrate different programs and protocols (e.g., by using common models provided by RDF ontologies such as SIOC, all kinds of APIs and gateways), but they are not used any widely. See the "pipes and communication" note for more on the topic.
There are less common issue trackers that are distributed, like bugs everywhere. Perhaps worth trying, the description looks nice.