As far as I know, Joplin is not really real-time collaborative, nor federated. I was using it a few years ago and I like it, that would be a great suggestion for people not interested in those two things.
why you wouldn’t hop on projects already out there
Ah... that's... yeah, that would probably make a lot of sense. I think that to us developers it's much easier to come up with our own ideas than to hop onto other projects unless they align very well with our vision. It's quite unusual to find other people with our very same goals. I'll be honest, I code for fun. I would like to build this tool because want it more than because I need it, as there already are both Google Keep and Joplin after all. If there was an alternative out there with most of the feature features I need, in a programming language and framework that I am familiar with, I would probably have joined or forked it. But no, unfortunately that's not the case. My goal is not to just find/build a replacement for Google Keep, my goal is to find/build a framework that can be used to build more collaborative apps in the future. A replacement for SplitWise is my next goal immediately after Google Keep, and I assume (hopefully not too naïvely) that once I will have a starting point, making more similar apps will be virtually free in terms of time required.
Actually, I was just so incredibly lucky that the Matrix protocol seems to overlap almost exactly with all the things I had in mind. I had included a few more features in my draft for a custom protocol, but honestly adopting something already made would save many tens of hours of work, so joining something already existing sounds like a good idea. I don't think I will be able to contribute code to it though, as it's developed in a language I am not familiar with (yet), so if I decided to go for Matrix after all, I will just be joining as a consumer.
LibreOffice also has Async collab [...] might also benefit from another person putting their time towards it
Oh, that's actually good to know, thanks! Personally, at the moment I use Google Docs when I need to work in real-time on a document with someone else. In my opinion it's just too convenient to just be able to share a link which can be opened with a web browser from any device and operating system. There are some good self-hostable web options for documents imho though, which are probably less resource-demanding than LibreOffice.
Unfortunately I am not interesting in contributing to LibreOffice. I have installed it on all of my devices, but I almost never use it.
Whatever you choose to do, I’ll be super interested to see the results.
I'll take that as an encouragement! Thanks!
Personally, I've been sharing this folder across different installations for years, even between different operating systems. I've never had any major issues so far.
The only minor annoyance is that whenever I switch between Windows and Linux I have to restart the browser once, otherwise extensions do not load on the first run.
So yeah, I would say diy-syncing this profile folder is feasible and very reliable. Same thing is true for Thunderbird, but I've been doing it for less time. And I would assume the same thing is also true for Chromium-based browsers because I do it with Signal which is Electron-based.