This tool is so expensive. I want to use it but for this to be an alternative to Notion you'd have to pay for Sync and Publish, which would come to $24/month. That is very pricey for many people.
Sync - On iOS, you can use iCloud to sync your files between your Mac and iPhone. I imagine that there are more configuration options for this on Android.
Publish - lots of different ways to deploy your notes to a site. There's one repo that helps you publish with Mkdocs [1], and I'm sure there are other tools the community has created to solve this problem.
It may not be as simple to set up as Notion, but that's the price you pay for wanting a solution to be cheap, private, and let you own your own data.
Use iCloud/gDrive/dropbox for synching instead. Never had any issues.
You can choose to sync via pretty much any sync solution like Dropbox, iCloud, Git, etc. For publish you can static site generators like Jekyll, Hugo, etc.
Edit: Today I learned there is iCloud for Windows, so you can point Obsidian to the iCloudDrive/Obsidian folder.
Going to give it a try.