I didn’t knew rclone was available on Android, thank you !! I will definitively try this ! :-)
I saw there is an app to start Termux scripts with Tasker :-)

Thank you very much for the very detailed answer !
It seems well thought. It may require some work (through time) but the result seems very good, with nice security and usability.
I’ll work on the first steps in the next months.
I don’t have kids yet so I can break it all !!

Thank you, it seems a good setup.
Can you explain how you did this securely ? Is the box with Pi-Hole / searxng / syncthing insiste a DMZ ?
I’m woried of a potential breach of my home network. If ports are open to the internet, and I miss an update (or if there is a 0 day) on the serveur box at home, it could be hacked, data stolen, and be used as a jump box to attack the rest if the network; so I want to be sure to do it right, it scares me a little !

I don’t really trust the server side encryption, admins can probably access files. I would sleep better with E2EE :-) But it can be right for some people, thanks for mentioning it.

I’d like to use Cryptomator (I have it on my phone), however it does not support the DocumentProvider API.
Because of this, using files inside a Cryptomator vault is very problematic with some apps. It is only possible to select a file in Cryptomator, and open it in an app. It is not possible to open a folder (unless I missed something).
For example, as far as I know it is impossible to open an Obsidian vault (a folder with markdown files linked between them) in Obsidian, if files are in a Cryptomator vault (and Android). It’s only possible to select one file in Cryptomator, and open it in some app. Same problem with some other apps.
Instead of using files inside the Cryptomator vault, an alternative could be to send a copy of local files in the Cryptomator vault. But because of the lack of the DocumentProvider or automation app support, it does not seems possible to automate this copy…