Minetest has no native gamepad support, but even on Android there will be keyboard & mouse support. To use a controller you'd map your controller buttons to the appropriate keyboard/mouse keys (not to the touch screen). I've done this on a Linux handheld with a touchscreen & it works great. I wind up using "hybrid controls", where for some crafting-related things I use the touch screen & everything else I use the gamepad.
If you go this route you'll a keymapping software for Android. I don't know of one unfortunately, but here's a thread discussing options.
If you're trying to run a keymapper to use a gamepad for Minetest then no, I don't think you'd need to make any Minetest settings changes. On a similar Linux setup I didn't need to make Minetest settings adjustments for this.
I'd expect that you'd need to start your keymapper program first, map the keyboard to your gamepad appropriately (i.e. wasd would go to the left analog stick, etc), check that it's working in a simple app like a text editor. Finally, if all of that works then try loading up Minetest.