It’s strange that NixNote would export to ENEX format, but make it different enough that it won’t import in other apps. I’ve added some info to the readme about it, as the recommended way would indeed be to sync with Evernote and export the ENEX from there.
The last time I tried Evernote was working with Wine too.
I’m using Nixnote2 and the export file is now “.nnex” without any other options available. Needless to say, this negates this entire process, making importing Evernote data strictly on a Linux box moot.
Just to add that one important distinction is that the NNEX export format does include the note GUID which would be needed to turn Evernote note-links into Joplin ones, unlike ENEX. For those of us extensively using the note linking feature, being able to import and keep those links would be a life-saver.