Welcome to Manjaro forum @thestranging
Kernel headers and dkms should be installed before building the driver from AUR
pamac install linux66-headers dkms
pamac build snd-hda-macbookpro-dkms-git
GitHub - davidjo/snd_hda_macbookpro: Kernel audio driver for Macs with 8409 HDA chip + MAX98706/SSM3515 amps · GitHub
This is a kernel driver for sound on Macs with Cirrus 8409 HDA chips. Sound output is now reasonably complete and integrated with Linux. Sound input still needs work.It will play audio through Internal speakers or headphones.
The primary audio should be set to Analogue Stereo Output in the Settings Audio dialog.
Sound recording from internal mike and headset mike is not yet fully interfaced with Linux user side.
The recorded sound level is very low but this is the sound level as returned in OSX. Amplification will be required eg using something like PulseEffects.
The hardware device sound format is limited to 2/4 channel 44.1 kHz S24_LE S32_LE. As long as use the default device volume control, other formats, frequencies work.
NOTA BENE: The direct hardware device (hw:0,0) and plughw:0,0 device have NO volume control so will be VERY loud!
Currently this works with MAX98706, SSM3515 and TAS5764L amplifiers. It will NOT work with other amplifiers as each amplifier requires specific programming.