What should happen
8BitDo makes various gamepads/controllers that are very popular. SDL (and thus Steam Input, SteamOS, any platform) has support for these natively since quite a while.

Implementation would require two gamepad icon variants per controller, as the devices of 8BitDo have multiple modes of operation: Xbox style and Nintendo Switch style input.
Afaict the gamepad icons for the two 8BitDo gamepad icons, can be copied from the Xbox One and Nintendo Switch gamepad icons. Only requiring new artwork/diagrams for the two 8BitDo modes.
Checklist