Error: nmap unable to open ethX

It’s pretty much straightforward, this error is less showing on Linux as they don’t have much problems with multiple packages as Windows do. Additionally, it’s much simpler to troubleshoot on Linux as the interfaces actually named that way.

On the other hand, when you get this on Windows OS it doesn’t make sense because the naming is completely different.
However, in most cases I got this error it was basically a corrupted npcap package, or a difference version installed with one software (many software use npacp) and causes one or more files corruption / damage.

So, simply remove and re-install the latest npcap on the system and it should solve the issue.
I just recalled this as I was reading the happy announcement of Nmap release (7.90) along with Npcap (1.00).
Yep yep, horray….:) Finally the Npcap has been released an no longer a beta version.