Did a little more testing this evening, here's the results. From the book I mentioned (converted from AZW3 source to Epub3 in Calibre), here are examples of how the many thousands of endnotes are linked throughout the book. Nothing extraordinary in the HTML, but no epub:type attribute, and no <aside> element. You can see that readers handle this case (a large endnotes page) in various ways: some display the specific endnote, others just take you to the page. It would be awesome to make this user-configurable, as FB Reader and KOReader do.
An in-page, superscript link to an endnote:
EPUB version:
<a class="note_link" id="Ants757-1" href="part0029_split_000.html#Ants757-1a"><sup class="frac">1</sup></a>
AZW3 version:
<a class="note_link" id="Ants757-1" href="part0029.html#Ants757-1a"><sup class="frac">1</sup></a>
The endnote being linked to (this is contained on a full HTML page with end notes):
EPUB version:
<p class="note"><a class="line_link" id="Ants757-1a" href="part0028_split_003.html#Ants757-1"> 1</a> <span class="text"> Adam</span> name evocative of the biblical first man</p>
AZW3 version:
<p class="note"><a class="line_link" id="Ants757-1a" href="part0028.html#Ants757-1"> 1</a> <span class="text"> Adam</span> name evocative of the biblical first man</p>
Here's how each reader device handles this specific end note:
Kindle Oasis: popup window
Kindle (web): navigates to the notes page
Kindle (android): navigates to the notes page
Google books (android): popup window
Google books (web): navigates to notes page
FB Reader: popup window
Moon+: popup window
KOReader: popup window
Calibre: popup window
Kobo Forma: navigates to notes page
*Note: as mentioned earlier, only with the Kobo: if you go to a later note in the Act/Scene of this play, which would be near the end of the end notes HTML page, then the Kobo will display it as a popup. For example, I click note "109" in the same Act, and it displays as a popup along with the contents of notes 110, 111, 112, and 113.