Radicale-DecSync VS Matrix-CRDT

You can use Tasks.org + DecSync CC + Syncthing to synchronize your data to a PC. There you would set up Radicale + Radicale-DecSync and then point a CalDAV client at Radicale (disclaimer: I have never tried this myself)

For calendar I would say: https://github.com/39aldo39/DecSync + https://syncthing.net/ and for sharing with someone you would run some web client on VPS talking to https://github.com/39aldo39/Radicale-DecSync

DecSync is good but there aren't any software that can read the folder containing contacts, calendar and tasks unless you use the version of radicale that supports DecSync which at this point isn't p2p anymore. So that way you can connect Thunderbird to it.

Another interesting and peculiar approach would be to use Matrix, which is chat and collaboration framework that is completely decentralised. Essentially, in this way Scrivano would translate pen input into chat messages that are sent to other users who receive them in real time. One advantage of this approach is that the collaborative notes will remain accessible even after you go offline and multiple users will be able to collaborate on a single note just like they would in a group chat. There are already apps that make use of this idea (e.g. see Matrix-CRDT or TheBoard), but when I tried this it last time didn't work very well and I'm not sure whether this is a limitation of the service or of the specific implementation I tried.

1. This is complicated. There is a notion of power_level, which you can set to different events. So you can set "send message" to power level 30, and any user with a "power level" of 30 or more will be able to send messages. Those power levels (and the required level to send an event) are granted by the room creator.

There is, however, no power_level associated with reading messages. I think you need to be joined to a room to send messages, and to be joined, you need to be able to read messages by design. So the "inbox" model doesn't seem representable to me. But maybe I'm missing something!

2. Yes. Events can refer to prior events to modify them, e.g. you can "edit" a previous message by appending a new message of type "msg.edit" (made up type, not sure what the exact it), specifying the old message id, and the new text. For matrix-based CRDT, see Matrix-CRDT[1], a Yjs backend using Matrix.

[1]: https://github.com/YousefED/Matrix-CRDT

Have you checked out Matrix? It's specifically a protocol (they've used OpenWhisper) but people are using it like a social media platform (specifically like IRC). There's even people doing google docs like services. I'm going to link a HN thread from that last link because others are just talking about Matrix and that'll likely be helpful to you.

Show HN: Matrix-CRDT – real-time collaborative apps using Matrix as backend\ (2 comments)