LibreLingo - FOSS Duolingo alternative

LibreLingo's mission is to create a modern language-learning platform that is owned by the community of its users. All software is licensed under AGPLv3, which guarantees the freedom to run, study, share, and modify the software. Course authors are encouraged to release their courses with free licenses.

Course templates are fairly easy to make it seems. There are a handful more not listed in the linked URL (though I think you need to install a local copy for them to work; links here are hosted by an old version of LibreLingo).

Edit: I have twice now changed the link, as I keep linking either the old or broken web interface. apologies, that's on me.