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]

[0] https://standardnotes.com/

[1] https://obsidian.md/

Also check Andy Matuschak's "Evergreen Notes" project https://notes.andymatuschak.org/Evergreen_notes

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.