[erichurkman]

https://agenda.com fit the bill for me. Offline use (though can only sync today through iCloud and Dropbox, I think, which sucks - but you can sync folders manually), pulls calendar from your system integration, simple payment. You can link your daily agenda items/notes to calendar invites.

Though it does not connect to email, at least today, which was OK for my use cases.

[eitland]

Agenda is super interesting, especially their payment model.

For some reason I don't end up using it but I have paid for upgrades once or twice after realizing that, voluntarily :-)

[nixpulvis]

I should mention I am running Wayland, and would like to continue to do so, ideally on my phone as well one day.

[vladsanchez]

Thanks for sharing.