Unfortunately, filtering does not work like that. Especially with high-frequency noise.
The filtering has to be close to the load to be effective.
This means that you would need such a filter really close to every device that you want to protect. Or at least between the device and the source of the noise.
By sticking it somewhere randomly, you could get some improvement if you are lucky, but you will most likely still get lots of high-frequency stuff on your devices. The amount of the effect will of course heavily depend on the level of optimization of your device's psu for high frequency stuff.
I used powerline adapters for a while, but I got some nasty cracking noise on my speakers so I got rid of them.
I now use only ethernet or wifi