Would it be possible to make a decentralized agenda protocol?

What if all my devices, my laptop and phone and tablet could talk with each other and synchronize my agenda point instead of trust Google or Apple iCloud to store and forward my agenda points?

I know @protonprivacy has an agenda app now, but it is still stored on a central server.

I wish there was a way to #p2p exchange agenda items, and maybe store an encrypted backup externally. But that backup isn’t used for synching.