Weird question, I know. My apartment comes with a modern/router combo that, for whatever reason, does not have an Ethernet port. So a friend advised me to purchase a modem, then connect it via coax cable to my apartment’s modem/router, then connect that to my PC via cat5. I did so, but the Ethernet connection on my PC shows no Internet. Is this possible to set up? Is there a software related step I’m missing to complete the connections?
Ethernet only helps if there is interference or distance causing these issues.
For a desktop pc distance won't change.
Interference comes in many forms. Other WiFi devices, Bluetooth devices (especially if the PC uses the same antenna for WiFi and Bluetooth), weather, microwaves, washing machines, dishwashers and anything powered by electricity that moves/rotates.
If your low speed coincides with these issues ethernet will help. Ethernet will also help with total speed, if WiFi is the limiting factor. Such as your fibre line provides 200mbps, but with limits the access to 120mpbs.
If your low speed doesn't coincide with a WiFi interference. It could be due to the internet supplied by your isp. You many need to contact them to run diagnostics on the line. You can check the speed if your able to log on to your routers web page, the router should have a website that is a series of numbers and a different user name and password to access this when your are connected to it's WiFi network.
Back in the bad-old-days of having a shitty provider in student housing, I had a similar situation, and solved by making a box-of-faraday with a carboard box and tinfoil. Popped their crap modem inside, put my slightly-less-crap modem next to it, and ran my functional CAT5 (yeah, it was a while ago) out of the box. The tinfoil creates a nice interference-free zone, where nothing but your own two devices exist.
Of course, this was also before my phone had wifi, so it has it's downsides, unless you want to add a third accesspoint outside the box.