My case - Ubuntu 18.10, 64 bit, Realtek r8169 ethernet adapter. I had no problem with it until i edited connection name in connection manager from netplan-enp3s0 to something more understandable. After that in resuming from suspend there is no connection at all. Restarting of network-manager doesn't help.
It seems problem is with driver
I found solution in internet to put in /lib/systemd/system-sleep executable file "network-adapter-driver-reload-after-suspend" contains
#!/bin/sh # This is a band-aid solution for coming out of suspend mode # to reload the r8169 driver for a Realtek r8168 network adapter ic. case $1/$2 in pre/\*) ;; post/\*) rmmod r8169 sleep 5 modprobe r8169 ;; esac # End Of File
which should automatically execute at resume and reload adapter driver.
Problem is that manual executing of "rmmod r8169" and "modprobe r8169" by root in console DO fix problem with network, but this systemd based solution does nothing.
I checked permission and attributes of network-adapter-driver-reload-after-suspend and should work, but nothing happens.
Needless to say i quite disappointed wit how fragile Ubuntu became since i never ever had such problems on previous version on same hardware.