Undo changes introduced by 3a7c49e: DontResolveLayers .
When deciding if a layer is localized we need to read Layers.

There's an issue with the latest qfieldsync release regarding localized datasets:
It's not showing the option to upload shared_datasets in the dialog and therefor it's not creating the shared_datasets project nor uploading any files. I could narrow it down to the get_localized_dataset_files function:

        for layer in layers.values():
            if not layer.dataProvider():
                continue

The problem is with the code change in 3a7c49e we don't resolve the layers and they then don't have a dataProvider so we always go out of the loop.

When disabling:

        if Qgis.versionInt() >= 32600:  # noqa: PLR2004
            # read_flags |= Qgis.ProjectReadFlag.DontResolveLayers
            read_flags |= Qgis.ProjectReadFlag.TrustLayerMetadata
            read_flags |= Qgis.ProjectReadFlag.DontLoad3DViews
        else:
            # read_flags |= QgsProject.ReadFlag.FlagDontResolveLayers
            read_flags |= QgsProject.ReadFlag.FlagTrustLayerMetadata

everything seems to work again:

• Shared datasets are identified
• Option for uploading missing shared datasets is shown (visibility is set to True)
• When checkbox ticked, the project gets created/uploaded, a shared_datasets project is created and the shared dataset uploaded as well.

I'm unsure if we need the layers for