Great question @Mark_S - similar to my ongoing quest to have a wiki for my small team (6 of them). I do a LOT in TiddlyWiki for work (project management) already, but I can’t extend it to my team. That means I use extensive and customized workflows for my own projects, but for my team I have to fall back to OneNote or PowerApps or other 3rd party stuff I dislike. I can’t tell what kind of experience it is on the back end, but the writeup uses the terms “small-team collaboration”, “auth to log in users”, “individual tiddler locking to prevent overwriting” etc.
The closest to this I’ve found is BOB, but that’s LAN only so nobody can use it from their phones easily or from home. I discussed this a bit in Saver options and combinations - Discussion - Talk TW (tiddlywiki.org), but didn’t find something else yet that would work. @saqimtiaz mentioned Tailscale which I was excited about until I tried to implement it and I had to install software on each machine. At work we don’t have admin access, so it has to be just point to url essentially.