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Carnet is one I like, though it's quite early in its development cycle (started less than one year ago, I think). Author is supported trough donations. It also syncs with nextcloud (and is available as a webapp --nextcloud or standalone), and explicitly takes google Keep as an inspiration. The desktop version has a barebones google keep import feature.

I've been on the lookout for such an app as well, and after trying a lot of different ones, this is my favorite so far.

Omni Notes is the best Google Keep replacement I've found yet.

You're right though, it's surprising how hard it is to find a note taking app that's just simple and intuitive.

Zoho notebook might fit your bill - its basically a keep clone