Released a couple of hours ago by Switch modding scene member Plutoo, nx-btred is a Bluetooth audio driver/redirector for the Nintendo Switch.
Plutoo explains that their solution works through the audrec:u service so as to record the game audio and subsequently outputs it on the new audio Bluetooth driver introduced in firmware version 12.0.0.
As such, this mod requires a Nintendo Switch on firmware 12.0.0+, as well as the latest Atmosphere and MissionControl to be installed, in order to function.
Of note, only games audio can be recorded and not the system applets due to a limitation of the audrec:u service.
Head to the Github repository below to find a link to the files required to download nx-btred and a set up guide.
nx-btred Github repository