Thanks for taking the time to explain. I didn't know how Penultimate worked previously.
Personally, I'd be fine with a 2-way sync where Penultimate (that is submitted to Evernote platform) confronts the modified-at time and simply replace its own notebook version with the EN one, if that's more recent.
However I see that Penultimate is pretty abandoned. I reported (1-2 years ago?) a bug about Penultimate (freshly installed) not allowing to create new notebooks because I already have more than 200 on Evernote side (but there is only the default one on Penultimate side). I see in the Apple Store that Penultimate was updated but apparently my bug report went ignored.
Also I tried different features and the app is broken in too many aspects (bug-wise and usability-wise), hence I'm not able to use it even in case the sync would allow non-readonly notes.
I've tried Noteshelf yesterday, before giving up and trying Penultimate again.
They aren't in a better spot:
it crashed the first time I run it.
crashes about 20% of the times I use it
sync is broken-ish on Noteshelf side
it doesn't preserve a local version of notes synced to Evernote (so if I have no internet, there's no way I can modify a note that was available just before closing the app)
half of the times it gets stuck while downloading the notes from EN
synced notes are broken on Evernote side
after a sync I can see the note being created in Evernote app; unfortunately the content is displayed only the first time after being synced.
If I come back to it later on, it shows nothing, there no content, apart for a pale blue background and the "View Only" tag. No app restart helped.
This happens to ALL the notes created with Noteshelf; other notes (manually added or sent from Apple Notes) are working flawlessly instead.
the thumbnail doesn't get updated when the content changes
the EN WebApp instead at least sees the updated thumbnail, but it still displays nothing as content of the note.
funny enough... the correct revision is present in the note History; it's the second-last-revision. Too bad that Evernote shows me the last-revision instead (the broken one, that I don't understand why is even created)
Their Evernote sync is so unreliable (sometimes it syncs, sometimes it doesn't).
I'll probably ask Apple Store for a refund of the 10 bucks it costs.
The sad thing is that I cannot find a working product among all the choices there are...
I dunno if I'm being particularly unlucky here.
Unfortunately Goodnotes doesn't allow to edit notes that were already synced. I tried that workflow in the past, but too often I find myself editing notes, once, twice, many times.