This article shows how to add a map from MapTiler Server running on-prem or offline into Tableau:
Get Tableau TMS from MapTiler Server
Open server admin, select a map, scroll down to the map detail, and download the TMS file.
Import own map into Tableau
Now open Tableau and import the TMS file here. Open Map -> Background Maps -> Manage Maps...
Click on the Import... button
Import your TMS file and enjoy the beautiful map running from your own laptop or server.