I see this discussion that one can change the default QGIS project format back to the text based
.qgs. But there is no detail. Quoting the discussion:
There is an option to start QGIS with another default setting file
You can have a look at how the french ministry of ecology handles this issue here: http://www.geoinformations.developpement-durable.gouv.fr/qgis-package-3-4-2-pour-test-a3662.html
But the linked page does not mention .qgs.
Does any one have a complete answer on how to change QGIS 3 default to use the old
(as of QGIS 3.12, Ubuntu 18.04).