Wired connection continously connects and disconnects

[stefabat]

I followed this solution:

Network Manager Stops Working Every 30 Minutes or So

I have the problem of Network Manager stopping to work every 30 minutes or so. I tried everything; even fresh install did not help. When it happens, Network Manager does not show any LAN or Wifi connections. When I restart the system, problem gets resolved. But after 30 minutes, same thing happens. I downgraded the kernel from 5.8.1-3 to 5.4.58-1 (LTS) and uninstalled all other kernels, but the problem is not resolved. I tried with connman too, problem did not go. Please help.

and it somehow worked even though I don’t know why.