The board in the top left provides the power. The board on the right carries the juicy stuff:

Bluetooth Module featuring the CSRA64110 Mono Audio Module with its antenna running along the top edge of the PCB.

The chip found in this video from "This Does Not Compute" in the 2018 model was a CSR64215 and in theory capable of aptX and stereo output—seems IKEA switched to the CSRA64110 in later models.

STM32F030 microcontroller featuring an Arm® Cortex®-M0

TAS5731M Stereo Digital Audio Power Amplifier from Texas Instruments

PCM1808 Stereo A/D Converter from Texas Instruments

Consonance Electronic CN3704 Standalone Li-ion Battery Charger