Not explicitly music related, but a potentially important tool for other parts of your life: https://sandstorm.io/
I had to share because I honestly feel like this is one of the most inspiring tech startups out there (Discourse is another favorite). They make a web app platform that is: free, secure, open source, self-hosted, easy to use, and pretty solid. There are definitely some clunky moments and things are not super well-polished at the moment, but I fully support what they are doing and I want to see them succeed. I'm running all of the internal informational infrastructure for a 6 person company off of a single digital ocean droplet with Sandstorm, and things are working out so far.
In particular, we really like RocketChat (self-hosted Slack) and Wekan (Kanban board (ie Trello)) for work stuff.
The big thing for me is that now you don't need to spin up a bunch of different VMs (or Docker containers) to just try out a self-hosted web app. I'd love to see more things ported to this environment. They deal with all of the security and authorization for you, and as a non-developer the 1-click install is a huge plus.