I've tried Obsidian+SyncThing, custom DIY apps, turtl, simplenote, Zim, probably others.
Nothing I tried was quite as frictionless on mobile as Keep, and the wear OS tiles are great.
Contextualise excels at organising information-heavy projects and activities consisting of unstructured and widely diverse data and information resources.
Contextualise is open-source: https://github.com/brettkromkamp/contextualise