Answer
Tableau Desktop 2022.2 or later
- Select Map > Background Layers.
- Select the WMS map layer you want to use.
- Select Make Default.

- Select Map > Background Maps > Set As Default.

The above operation will ensure that the selected layer will be displayed the next time you open Tableau Desktop.
*This operation creates a tms file with the settings saved in the "Mapsources" folder in My Tableau Repository.
Tableau Desktop 2022.1 or earlier
Although it is not possible to perform the same steps in earlier versions of Tableau Desktop the update can be accomplished by using a similar TMS file created with Tableau Desktop 2022.2 or later.
Note: While a .tms file may be helpful in connecting to your map server, Tableau does not test or support .tms files, and success may vary.