Good news everyone.
I was able to solve my sleep-less issues
I updated to OpenCore 0.7.0 and replaced the existing
FakePCIID_Intel_I225-V.kext and
FakePCIID.kext with
a new one from this post. Moreover, as described in the post, I removed the
Intel i225V entry from my
config.plist under DeviceProperties.
After rebooting, the machine works just fine, the Ethernet card is up and running, sleeping works for the very first time (
even the fans, screens, and RGB-LEDs switch off) and
I wake the machine by touching the keyboard (even the wireless Apple bluetooth keyboard). This freaking awesome!
After investigating the situation it looks like the main difference in the kext is:
XML:
<key>IOPCIPrimaryMatch</key>
<string>0x15f28086 0x15f38086</string>
and well, the upgrade from OpenCore 0.6.9 to 0.7.0.