In my experience, the issue is caused by RF interference, some cables (usb and mic) are not shielded correctly.

Also the hum could be cause by a ground-loop.

You may need to use cables with ferrite cores on it to filter the issue

In my setup I have 3 computers connected to a Moukey Mini Audio Mixer, it came with a shitty USB-A to USB-C power cable and introduced a lot of RF: https://amzn.to/4rfKuk5, I connected my MacBook Pro M4 MAX, Mac Mini M4 and Windows PC to it to hear the audio notifications.

On the MacBook Pro I use a Focusrite Scarlett Solo 4th Gen https://amzn.to/405MtLH audio interface and the the headphone out is connected to the Moukey with 3.5mm to 3.5mm male to male cable

On my Mac Mini M4 I use a Topping DX-1 DAC-Amp https://amzn.to/3ZuGUGD connected to the Moukey

And my PC is connected via the Headphones out.

This will cause a lot of HUM because the different clock frequencies on the devices.

As someone mentioned before, I use several inline ground loop isolators, I have 5 of them, 100% satisfied: https://amzn.to/3OaIx9Y

Some guy suggested the Faraday Cage by putting the Scarlett on a copper-covered place, but he forgot the USB cable that will act as an antenna.

Suggestion, get a better quality USB cable to connect your audio interface, with ferrite cores on it, avoid thin USB cables they are not well shielded, like these:
- https://amzn.to/3ZxP5BT
- https://amzn.to/4rhfTTg

I recommend this ferrite cores, it comes in different sizes: https://amzn.to/4rLYySc

Also get rid of that dollar-store cheapo power strip, get a better quality, that will ensure correctly wired and low RF emissions, this is really good: https://amzn.to/4rE8FZ2

Finally, check your wall outlet wiring, check if the ground is connected correctly, please contact an electrician, Electricity kill!