When multiple users edit the same GeoPackage project from QGIS desktop via qfieldsync, there's currently no real protection against one user's sync overwriting another's changes.

QField mobile already has a real conflict-resolution mechanism for this class of problem, but qfieldsync doesn't participate in it. Using postgres instance to deal with that problem could be a solution but in some cases it's more inconvinient than it seems to be.

I needed a fix quickly for self hosted deployment and prototyped a stopgap:

the desktop client remembers the file version it last synced, sends it on upload, and the server does something similar to a three-way merge of the GeoPackage instead of overwriting.

It works, but I wonder if building a separate custom system instead of reusing your existing delta/conflict approach is a good final architecture.

Is integrating the desktop client into your delta pipeline something you're planning? If you're open to it, I’d be happy to contribute and start off a discussion on how to approach it.