I've installed Factorio 2 Space Age across multiple machines (Ubuntu 22.04, Fedora 40/41) and cannot auto-update on any of them. Manually checking via "About" reveals "No updates available"

For vanilla games 1.1.x and 2.0.x auto update worked and still work without issues..

My current way to update is to get informed by others I need to update my dedicated server, log in on GOG, download the installer and run it on my current installation (sometimes creating a nested Factorio folder..)

Installation method is the downloadable installer for all scenarios (no GOG Galaxy)

Ok, my fault - I guess I did, what's being described in the post

STICKY: How to Update Factorio to the Latest Version (Guide) (sorry, can't post links)

..in the past with Factorio 1.1.x, but I didn't remember.

So just register your "Space Age" key you find in the CD-Keys section below GOG/games/Factorio on factorio.com in your user section and you'll get your upgrades even when GOG doesn't have them yet.