Here's an easy solution for keeping your Ethernet ports free from dust and other unsavory particulates. These squishy Silicone RJ-45 Dust Cover Inserts slip neatly into any computer or device with an Ethernet socket, from the Ethernet FeatherWing to the Raspberry Pi 4. 

Comes in a pack of ten, so you're set even if you have a hub with a lot of ports, or if you lose some.