For anybody still looking for this, or wanna improve this method, try this. Ive done some research about the best way to do the remote vault with GitHub.
First of all, On PC, use Obsidian Git community plugin in the Obsidian. It have auto push and auto pull feature. Nice. So now I can write notes in obsidian, it will auto sync to GitHub.
Now how about if I wanna access it in mobile phone? After 1 day searching, the best way is by using Termux, no other apps as simple as Termux. The same as the main answer in this post, but simpler. At first, I thought “I need to to git clone, then create some automation script to git push and git pull whenever I want bla bla bla”. Turn out its much simpler than that.
I use Termux. Setup the storage path. Install git, then git clone my repo, with username email and auth token and stuff (you dont need to install gh, setup ssh, update upgrade, cronjob or anything, the only command you will use ONCE, is only git clone). And then open obsidian on mobile phone, find the vault folder u cloned into your phone. And then, the magic happens, the Obsidian Git plugin from PC is there too!! Its downloaded along with the repo. At first when thr Obsidian Mobile App is emtpy, u cant setup any community plugin. But after u have at least 1 vault set up, u can access the community plugin.
And now, you dont ever need to touch Termux anymore! Because the Obsidian Git plugin on the Mobile App will automate the push pull for you, the same as PC.