To get the map working on dedicated server, you get to do like every other maps mod
(meaning: putting Workshop ID, Mod ID, Map in your .ini file)

WorkshopItems=2650315026
Mods=Backrooms2;
Map=Backrooms 2;Muldraugh, KY
(keeping Muldraugh, KY at the end is very important in any case)

And copy media folder of the mod in "pzserver\media\" like you would do for every other map

Then do as the following:
1) Deleting everything inside "Muldraugh, KY" folder
2) copy all the files from "Backrooms 2" folder to "Muldraugh, KY" folder
2) copy all the files from "Backrooms 2 (Escape)" folder to "Muldraugh, KY" folder
https://i.imgur.com/yZq5QBJ.png

Note:
I recommend to put the zombie count as "None" in the settings
If you're hosting your server on Windows server or equivalent i recommend to use a GUI such as Project Zomboid Server Manager avoid headache (especially when installing maps)