How can I control volume with a PS4?

I have a PS4, which attaches to a monitor through hdmi. The monitor then attaches to some speakers which have no volume controls.

I need to control volume, currently the only way is to navigate the monitor settings using its menu and brightness buttons. This is absurd.

The monitor is CEC compliant (https://en.wikipedia.org/wiki/Consumer_Electronics_Control), I can control it with my Mac and a CEC tool (https://github.com/the0neyouseek/MonitorControl).

I've already found that PS4's do not have a volume control built in.

Is there no plugin for this? No plugin for standard CEC control?

The only CEC control known for the PS4 is to turn on/off the TV when the PS4 is turned on/off.

It doesn't appear to have volume control, or any other control.