Gaia GPS includes a wide variety of map sources. This article will show you how to load your favorite map source in the app along with how to find a new favorite.
To change the map source:
Tap on the Layers icon.
Tap on your preferred map source, then tap back arrow to return to the main map.
To add additional Map Sources that do not appear on the default list:
Tap Edit Layers in the top right corner.
Select a category that fits your needs
Add map sources by toggling the switch to the right of each map source to "on". To remove a map source, toggle the switch back to "off".