Mind maps are really just nested lists right? https://workflowy.com/ is one of the best nested list (tree) editors I've found for mind-mapping and note-taking.

When I'm not using orgmode I usually use yED[0] for diagrams and graphs. Not specifically mind-mapping software, but close enough for my purposes.

[0]https://www.yworks.com/products/yed

Freemind is alright. Java. Does the basics. Runs everywhere. Open source.