iMac Losing internet connectivity frequently

Okay, please read to the end because you're going to THINK you know what the question is, but it's not the obvious things.

For about a month, my iMac (2019 model) has been losing connectivity frequently. Restarting the computer seems to be the only resolution. After a reboot it usually works again, though for the past few days that has been unreliable as well.

What do I mean by "connectivity? Well, I'm not sure exactly, here's the symptoms. The computer is hardwired to our router, Wifi is disabled. At no time will an error, or warning, notify me that the internet isn't working. But anything that requires an External connection simply sits idle forever. Web browser, connection to cloud drives, Discord or Zoom connections, anything.

HOWEVER. The computer can still stream media to other devices in the house. It is still clearly connected to the router, which is also functioning, as other devices can still access the internet via wifi, or ethernet connection.

iPad connected to router Wifi can still access internet. PS4 hardwired to Router can access internet. Both can access files stored on Desktop in question. So the router appears to be functioning correctly. The cable itself is also working. Everything is working! But still the desktop internet connection won't "work". It is connected. It thinks it's connected anyway. If I turn on WIFI it is able to connect to the router's wifi signal, but still won't actually DO anything external.

So yeah, I'm really confused as to what could be the problem... >_< Working from home, kids have remote classes, all that stuff during distancing measures, so it's a fairly critical problem. Any ideas?