Sorry for not having been more specific: Yes, with the above OpenWRT build, as of last night PT, my NanoPi R5C wouldn't detect eth1. Doesn't show up anywhere in the logs even.
With FriendlyWRT the interface shows up, so seems to not be a hardware issue.
Interestingly, I tried Debian for the device. It misdetects my device as R5S and two interfaces show up. If I manually apply the R5C config, then only one interface shows up. Wondering if that might be related. Details: https://github.com/inindev/nanopi-r5/issues/3 Maybe there are (slightly) different versions of the hardware?