• Create repo in GitHub
• Clone in directory where you want it (this is for PC)
• And in terminal, just make first commit and push. So plugin in Obsidian can do those easily next time.

Windows/Linux

• Set up ssh keys

• Install https://github.com/denolehov/obsidian-git
  Community plugin in obsidian (obsidian://show-plugin?id=obsidian-git)

• Configure plugin.. like username and email, but if there is ssh in OS, then no need to set up anything else.

Android

• Create empty vault
• Install same plugin on phone.

• Create git token:
  Minimal permissions required are
  "Read access to metadata"
  "Read and Write access to contents and commit status"

• Under the "Authentication/Commit Author" section, fill in the username on your git server and your password/personal access token.

• Exit plugin settings, open command palette, choose "Obsidian Git: Clone existing remote repo".

You just use http way of cloning in github (so it have .git at end of url.. )

Overide

• Then you can add username and email, to be synced...

In plugin settings, add it to be synced every 1 minute.
No notifications.
Auto backup after file change
Auto pull interval 1 minute
Pull updates on startup to be On
Push on backup to be On
Pull changes before push to be On

Docs