I'm using Google Drive to sync between my Windows laptop and desktop, and Android phone. It works very well.

In general you can use many cloud provider, SyncThing Fork or GitHub.

I wrote about all these options in more detail here: https://bryanhogan.com/blog/how-to-sync-obsidian

The easiest way to sync would be with the official Obsidian subscription, which costs the most amount of money from the options mentioned here.