I pre-ordered the game here on gog and after suffering through the release delay I am excited to finally be able to play...
And now that I am a bit into the game I thought its time to maybe go on one of those treasure hunts. But where are the maps? Not in Henry's trunk.
Did I miss them in some other place? Did we not get them? Anyone here found them?

the preorder dlc has a separate installer. if you have installed it, they should have been in henry's trunk in the mill immediately after the prologue.

Thank you! For some reason I either totally missed it last night or my Galaxy client didn't fully update to show it. Found it now though.
Now to hope that they get added retroactively to my save when I activated it *crosses fingers*

The treasure maps didn't show up till after you get a stash box. So look there after the game tells you about the stash box.

To access "Ancient treasure maps" you need to get to certain point of main quest. (1st access to your stash)