I have recently inserted Network Acoustics ENO Ethernet Filter between my router and very happy with the results. It’s probably the best ‘passive’ device out there that effectively lowers the noise floor within ethernet router and switches. I bought the Ag version package with LAN Ag cable.
https://www.networkacoustics.com/product/eno-ethernet-filter-ag-695-incl-vat/
Give it a try, it comes with 30 days return policy.
https://www.networkacoustics.com/product/eno-ethernet-filter-ag-695-incl-vat/
Give it a try, it comes with 30 days return policy.