USB 5V power filters or grounding my computer KVM to eliminate noise on audio introduced by keyboard

[duesentrieb]

I am using a Belkin KVM for years. I recently decided to route audio to my speaker though it. However, this introduced noise/hum. Tried several things, including getting a ground loop idolator for the audio going from KVM to speaker. However, this didn't fix anything.

After testing various combinations I noticed that the humm is gone when disconnecting the keyboard from the KVM. I am using a Logitech K740:

It is caused by the backlit function. If I keep the light at 100% or off no noise. The keyboard dimmer is causing this..

Is there a way to cure this other than to replace they keyboard?

I was looking for USB filters which exist. But seems like most filter more than 5V and filter data (e.g. for USB DAC applications).

Maybe something like this?
https://www.aliexpress.com/item/2251832570964632.html?gatewayAdapt=4itemAdapt
Can't really find anything in the US.

My Belkin KVM doesn't have a ground screw. So, not sure how to ground it and whether it actaully makes sense.

 

[Bluejets]

Use co-ax shielded audio cable.
Ground the shielding only at one end i.e. the source.

 

[duesentrieb]

I believe the noise comes directly though USB 5V and not though air.
How could I filter the USB DC?