Base Map Selector

[SethHiatt]

Maybe I'm missing something, but it seems like Instant Apps in general don't support adding a base map selection button.  Most of the time this is pretty essential for us, so I end up building something in Experience Builder.  Wish you could do just a little more in Instant Apps. 

[KellyHutchins]

Are you looking for the Basemap Toggle component or the Basemap Gallery?  Both are available in instant apps you can search by app capabilities to find apps that support each component.