I have pretty unreliable internet so I like to install via offline installers when I want to get back into a game I uninstalled to free space. I recently reinstalled this game and despite having the most recent installer version (1.19 hotfix) I was met with an automatic download of an update for 10GB on Galaxy. I can't find any trace of patch notes and Galaxy still says the most recent version is 1.19 hotfix.

Any insight on this? It seemed to download just fine. I have the Deluxe Edition.

Since you own the Deluxe Edition, Galaxy just automatically downloaded the Season Pass DLC. :)

Oh? But I installed the season pass stuff through the backups as well

Yeah, but for whatever reason Galaxy isn't able to recognise DLCs installed with offline installers. That's why the DLC got downloaded again.

Oh, okay. Thank you!

I have the same for several games with DLC, The Witcher 3, Metro Exodus etc.

You have to stop the GOG download for the game and check / repair the game files. The download will be much shorter ;)