module not loading on startup

[Gary Dale]

I'm running Stretch.

I had to replace/upgrade the motherboard on one of my computers. While 
that went fairly smoothly, I lost the network. Since the new motherboard 
had an RTL8168 NIC, I stupidly tried Realtek's module. Not my best plan.  :(

I eventually tracked the problem down to a UDEV persistent rule (now 
deleted) and also the need to modify /etc/network/interfaces to use the 
name the name of the new NIC (enp5s0 instead of eth0 - since it wasn't 
carried over in the upgrade from Jessie). However because I installed 
the Realtek module, the r8169 kernel module isn't automatically loading.

I deleted the r8168 module and renamed the r8169.bak to r8169.ko, 
updated the initramfs and even reinstalled the 4.9 kernel but the r8169 
module still need to loaded manually after boot, requiring the NIC to be 
brought up manually as well.

I realize I can just add the module to /etc/modules but that's not very 
elegant and the hardware probe should be able to load it like it used to 
before I screwed it up. Any ideas on how I can fix my mistake?