TRS - unbalanced stereo input in mixing boards

 Classic situation:

Spontaneous decision to feed music into a mixing board via a laptop.

In this situation, most people do not have a USB interface at hand to route the signal via two balanced outs to a mixing board.

What happens instead? They use the headphones out, which classically comes in a TRS configuration - unbalanced L and R out.

Once you feed this into a line in of the mixing board, the board combines both channels to mono.

Instead, there should be at least two line ins for a TRS configuration where L and R are recognised as unbalanced signals and routed to the correct channels. (Two line ins because you may want to stream sound from multiple devices, and one line in should be a backup.)

Right now, I have this exact issue working with an Allen & Heath SQ-16. It does not have cinch, so unbalanced tape ins via cinch are not a workaround option here. Maybe cinch to 6.3 mm jack adapters would work, but again, that requires a bunch of adapters. The more adapters, the higher the risk of equipment failure.