Uploading a new project with PostGIS layers to QFieldCloud creates a geopackage

Following behaviour has been observed on an on-premise QFieldCloud instance (don't know if it this can be qualified as a bug, and if it is a QFieldSync or a QFieldCloud related issue) : when pushing a new project to QFieldCloud with PostGIS layers, those layers seem to be converted to geopackage on the QFieldCloud instance. The idea is to use the "Hybrid editing" setup (https://docs.qfield.org/assets/images/hybrid-schema.png)

Steps to reproduce

create a new blank QGIS project
add a PostGIS layer to the project
go to QFieldSync window
click on "Create new project"
choose "Convert currently open project to cloud project (recommended)"
choose a name, description, owner, local directory and then click "Create"

In the QFieldCloud admin page, when looking at the project's Project details pre JSON, the layer is stored as a geopackage with a filename like /tmp/... .gpkg

Versions

QGIS v3.34
QFieldSync v4.9.1
QFieldCloud v0.27.0

Current workaround

There is a workaround I'm currently using, which consists of :

pushing a simple project to the QFieldCloud with just an OSM xyz layer
after project is created on the QFieldCloud, add the PostGIS layers to the QGIS project
synchronize the project to the QFieldCloud

After having done that, the layer is okay and is a PostGIS layer, with the datasource key and PostGIS connection value in the Project details pre JSON of the project, database connection is okay between the QFieldCloud instance and the PostGIS database

opengisch / qfieldsync