Radicale-DecSync VS DecSync

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.

A few years back I used to use SyncThing + DecSync for that purpose, and it worked quite well. Looks like it hasn't been updated in a while though.

https://github.com/39aldo39/DecSync

DecSync

There is decsync that works pretty good on Android. It stores contacts & calendars in a text file that can be synced with syncthing. There is a plugin for Evolution (Linux Mail client) but none for Thunderbird. But there is a plugin for Radicale, which is a caldav server. So you can run a local caldav server, connect Thunderbird to it and sync the decsync database with syncthing to your phone.

DecSync works with Syncthing to sync contacts and calendars.

I am a bit puzzled why so few people use DecSync and Syncthing for this?

I found some discussion here which is confusing when it says it wasn't designed to function this way when their own documentation seems to indicate otherwise.

I'm fine with either paying for software, or self-hosting something. If I go the self-host route, however, I would need to start and learn completely from square one. I saw some options in my searches that required software on my own server, but I wouldn't even know where to begin with that. DecSync came up in my searches, but based on the description I'm not sure if it would be linux only or not. (I'm on windows)