I use syncthing between my desktop and laptop for syncing all my documents, development environments and so on. Works well.
But how well does it work for sharing with someone else? E.g. it would be great to find a solution where myself and my partner could share notes and shopping lists which we can both edit. We use Google keep currently but I'm currently testing out solutions to de-google our lives. Nextcloud seemed like a good idea as it has docs and things but I've not found it very good to be honest. Especially syncing on a mobile. I've been using obsidian recently for my notes and it works well between laptop and desktop with the nextcloud app but I have to keep going into nextcloud on android to force it to sync or pick up new files. I'm just about to see how syncthing works for that but back to my original question..can you reliably have two people editing things with syncthing?