Mindmaps
https://www.mindmaps.app/
david+mindmaps@drichard.org
This app was originially developed by David Richard. He made the platform. But the development has been ceased by him a couple of years ago.
Mindmapmaker.org
app.mindmapmaker.org
The app hosted at mindmapmaker.org is managed by Azeem Cv. You can reach him at cvazeem@gmail.com
Mindmapmaker.nl
Dutch version of MindMapmaker.
This app is also managed bij Brainpartner ( same as www.mindmapmaker.net)