It is very likely that the HDMI port of the DeskMeet X300 is only HDMI 2.0, not 2.1.
This is because no AM4 APU supports HDMI 2.1 - neither the Ryzen 5 4650G Pro nor the 5600G or other APU models on this platform.

The HDMI controller is integrated directly into the APU. The mainboard (DeskMeet X300) does not extend the HDMI functionality, but only passes it through.
Tools such as CRU (Custom Resolution Utility) also show that the active output is recognised as HDMI 2.0.

I can agree with energy21's statement. The DeskMeet X300 'only' has an HDMI 2.0 connection.