Tried one more thing:
In Android file manager, I have created a folder called “Obsidian sync folder”.
When I have this as my vault, and DriveSync had synced, as explained above Obsidian crashed.
Then I created a new folder called “Test Parent”, and moved “Obsidian sync folder” into parent. Now I can open it in Obsidian!
Then I moved it back out of parent (exactly how it was originally). And Obsidian can still open it!
Then I started the sync process again. And after a while, in the middle of the sync, and when it had not even synced any files yet (because there’s nothing to sync basically, I have just moved the folder to another location and then moved it back again in my Android file manager), Obsidian suddenly crashed and now I can’t open it again!
So obviously syncing does something that crashes Obsidian, in 2 different sync apps now. And even after stopping the sync, I cannot open it with Obsidian. And even more, even after uninstalling both Obsidian and the DriveSync, and reinstalling Obsidian again, trying to open the vault with Obsidian crashes it!
Renaming the folder doesn’t help either.
But, again, moving it to another location, then moving it back again, then opening with Obsidian works!