Ah, yes, using the .env file makes sense. I've got only one database and so it doesn't matter. But I could see someone using different databases for different purposes (one for day trips, another for hiking?) and so need different maps.
But as I said, while writing it, I decided to move permanently to the mapbox tiles and have made the change on my install.
Say, what and how do you use different databases? Is your installation used by different people?