https://wccftech.com/notes-not-syncing-in-ios-13-and-icloud-you-are-not-alone/

Are your Notes not syncing on iPhone or iPad running iOS 13 or iPadOS? You are clearly not alone. A software update should fix this.

So it all went down like this - I created a new note in the Notes app on my iPad thinking that I would follow it up later on my iPhone So, I packed up, left home, and a few hours later, boom, no new note on my iPhone, and definitely nothing to follow up to. Came back home and the note randomly synced across all my devices, including the Mac. What sorcery is this?