Obsidian has everything your needs are, you can setup syncthing to sync your notes across multiple devices. Everything is a .md file and organized using folders and it has great plugin support. Though ability to publish from inside the app is locked behind a subscription. You can always use pandoc to just convert the md files, there probably are some plugins that try to do that. Also i love how lightweight it is.
Second is Nebo, Nebo is for handwritten notes usecase. This isn't something many people really have a usecase for, But Nebo has AWESOME handwriting -> searchable text conversion, specially for Math! And publishing things is as a easy as clicking publish. And it has google drive/drop integration for sync (I'd rather use syncthing but the android app doesn't expose the stored files).