The Android app deficiency is probably because Apple & Microsoft totally dominate the tablet market, and academics generally aren't interested in managing references on their phones ;)

Are there iOS apps?

Note that e-ink ereader tablets are often Android-based.

None are iOS based.

And those devices are not "phones".

(Most lack phone capabilities entirely, though there are also a few e-ink smartphones. I'm not talking about those here though.)

Zotero shipped their first-party iOS app a little over a year ago.

It looks like people are asking for a better reMarkable solution, and I'd love to see that too! In the mean time, the zotfile plugin has solid tablet-syncing features. It isn't slick like modern cloud sync services, but it's functional and fast when you click the button.

Thanks, good to keep in mind.

Though, again, I (and my archive) largely live on my e-ink ebook reader, and that is an Android device.