There's Standard Notes[0]. It doesn't have mind maps, but you can tag your notes. If you want something more complex, take a look at Obsidian[1]<p>[0] <a href="https://standardnotes.com/" rel="nofollow">https://standardnotes.com/</a><p>[1] <a href="https://obsidian.md/" rel="nofollow">https://obsidian.md/</a>
Also check Andy Matuschak's "Evergreen Notes" project <a href="https://notes.andymatuschak.org/Evergreen_notes" rel="nofollow">https://notes.andymatuschak.org/Evergreen_notes</a><p>It's not a software per se, but the way he organizes his notes is the holy grail IMHO.
Don't know too much about it but a lot of my students use Anki and seem to love it. Personally I like keeping it simple and just using a git repo with an update script running.