NOTE: As of version 10 of the Evernote Mac app, released Sept. 2020, AppleScript support is no longer available and this technique will not work. Details of options in the integration guide
As has been noted in the integration guide, Evernote’s SDK support on the Mac is not great preventing Drafts’ native Evernote action steps from being available on the Mac platform.
Evernote’s Mac app does, however, have good AppleScript support - and with the introduction of AppleScript support in Drafts actions, it is now possible to create cross-platform Evernote actions that use the native action step on iOS, and AppleScript on the Mac.
I created an example of the “Save to Evernote” action that ships with drafts demonstrating one way to go about configuring such actions…with the Evernote action step for iOS configured to only be enabled on iOS, and a script step running the AppleScript version configured to only be enabled on Mac.
There are many variations on this possible. This version does Markdown conversion, and saves to the default notebook to a timestamped note title…but could serve as the basis of more advanced actions.