Syncthing is free, open source software that can be used to easily synchronize an Obsidian vault between your computer and phone/tablet. Not only free, but completely secure, private, and blazing fast. Here are links to an article I wrote explaining how to use it.
- Biscotty’s Workshop not mobile friendly :-(
- Substack
- Medium.com
Resilio Sync works very well for this too. I had looked at syncthing, but there was a reason I chose Resilio. Just can’t recall what that reason is at the moment