It seems as collab package 1.13.5 is not the correct version for this version of Unity.
In fact to resolve it I have to manually upgrade collab to the current version: 1.15.1.
Is this a bug?
Extra unwanted packages in new projects (collab, testing, rider and other junk):
About the fastest way I have found to make a project and avoid all this noise is to create the project, then as soon as you see the files appear, FORCE-STOP (hard-kill) Unity (with the Activity Manager or Task Manager), then go hand-edit the Packages/manifest.json file as outlined in the above post, then reopen Unity.
Yes, in fact the other solution is what you said: editing the manifest.json file.
Anyway, I don’t really understand: don’t they have a testing team before releasing Unity versions? In which direction is Unity going? In the rush to release new features the quality of the editor is getting much worse…