Hi.

Unfortunately I was stupid enough to get the DLC High Resolution Texture Pack and now Galaxy keeps trying to download it even though I don't want it.

I also haven't found a setting to stop this permanently.

Can anyone help me?

Try the off-line installer for Fallout 4 only.
In Galaxy I also can not deselect the texture pack (under Manager installation/DLC).
It is checked, with no way to uncheck it.

Since I already have it installed and playing I report this to Gog as a bug. Steam also allows you to turn DLCs on and off. Must work here too.

Late reply but hopefully I can help, also attaching pictures for reference

Have you tried clicking the two lines button next to install/play in galaxy, going to manage installation and selecting configure

There will be a DLC tab on this page, if the High resolution is there, untick it and it should hopefully not download it
(showing different game in screenshot attached as I don't have the dlc for FO4)

Hope this helps anyone with this issue, good luck