@acelaya I don't have a very easy solution. I've seen "checkout from Git and change your tag", "Composer update," and self-modifying updaters (eg, Nextcloud, or the Platform.sh CLI app).
I think an update CLI command is probably the best option for non-cloud envs. In concept it could make its own backups and do the download for you from GitHub, using the API. Though that is admittedly more work.