On android 10 Joplin version 1.4.11 is broken while using local filesystem for syncing, for example, my case when using syncthing and different dedicated forlders in my devices for saving the Joplin database, on android once I put the right path, with all the permissions granted, and with the synced copy in place it sends me the error "Error:Directory could not be created" even with the folder "locks" created by the application in other devices.
This is not new and I have been doing some research and the problem seems to be that the android api (29) of android 10 is not on par or with the same standards for permissions than the one used in joplin which is android api 28 or that's what the debug section showed.
Here is what I first found which lead me to this I didn't try his method nor his solution since the app he mentions has a paywall, is not much but I wasn't expending anything on this, so I did some more digging and found out a way to manage permissions directly to the phone from the computer using adb, there I was trying to change or grant the permissions said in the previous post, adb didn't recognized the permissions, as shown in the pictures:
Then I went to the source code of joplin to try to understand what is actually the issue, I know some things of code and how to interpret it and read it but not developing myself, what I found was this which are the changes needed or pointed out by the android docs, thing is these changes are issued for version 1.5 and currently we are on 1.4, I could build it from source on android if I knew how to test it and see if it solves the issue.