How to switch to dark mode theme?

I would like the MainUI interface to be darkmode everywhere for all users all the time. How do I do this? It’s probably super simple, but I can’t figure out how to change from light mode to dark mode, and depending on the device visiting MainUI, which theme is chosen seems almost arbitrary.

Is there a setting for this somewhere?

In the “Help & About” menu option from the let-hand menu bar, you will find the theme options.

Ah, thanks! Will changing the theme from Auto to Dark change it on all devices, or will I manually need to adjust this for each device?

Just for the device you are making this changes.