Add support for MSI motherboard B450M MORTAR MAX (MS-7B89)

I have checked out OpenRGB and tried to make it work on my MB (https://www.msi.com/Motherboard/B450M-MORTAR-MAX). The MB data sheet says it has Mystic Light, but OpenRGB detects MSI-RGB. OpenRGB does 'something' on first try (like switching the LEDs to red), but subsequent actions fail and don't change anything.

Output of 'i2detect -l':

i2c-3	i2c       	dmdc                            	I2C adapter
i2c-1	i2c       	dmdc                            	I2C adapter
i2c-8	smbus     	SMBus PIIX4 adapter port 2 at 0b00	SMBus adapter
i2c-6	i2c       	AMDGPU DM i2c hw bus 3          	I2C adapter
i2c-4	i2c       	AMDGPU DM i2c hw bus 2          	I2C adapter
i2c-2	i2c       	AMDGPU DM i2c hw bus 1          	I2C adapter
i2c-0	i2c       	AMDGPU DM i2c hw bus 0          	I2C adapter
i2c-7	smbus     	SMBus PIIX4 adapter port 0 at 0b00	SMBus adapter
i2c-5	i2c       	dmdc                            	I2C adapter

Output of './OpenRGB --list-devices':

0: MSI Motherboard
  Type:           Motherboard
  Description:    MSI-RGB Device
  Modes: [Direct]
  Zones: 'MSI Zone'
  LEDs: 'MSI LED'

If there is anything I can try to help, just let me know or point me in the right direction how to add support.