Bit sure it's exactly what you're looking for, and I've never used the mobile app but I use the Linux and windows versions of Obsidian and just manage sync on my own. It looks like there is some built-in sync on the android version that might be worth looking into.
It's basically a nice interface on a collection of markdown files.
Obsidian isn't open source
Not sure on the etiquette, and if I should cross post to other communities? I'll wait a little and see before doing so.
Try MindMeister or TheBrain. Neither are open source, but they work on Android and one is ad-free.
Thank you.
Mindmeister was very sneaky and said I would have to pay monthly after my first month was up, with no disagree. Unethical interface design.
I then tried it, and I can't edit nodes. And it doesn't work offline. It's a hard no.
The brain I have no idea as registration won't continue and gives no errors. So I can't try it.
This is why I prefer open source, and no need for user accounts