Potentially, yes.

There is an open issue on GitHub to add an API. Once that feature is implemented, adding a web page where links can be submitted for archival becomes trivial.

ArchiveBox UI coming soon

Yup, I actually do this right now using Shortcuts.app on my phone to SSH into my server and pipe my latest bookmarks from Pocket into ArchiveBox!

It's a nice way to update my archive with one tap from my phone.

Could the intermediate step via Pocket be avoided, e.g. could the URL be passed directly from iOS to ArchiveBox?

Yes, easily. Just append the URL to a file with SSH and pipe the file into ArchiveBox, or pipe the url directly into ArchiveBox via stdin.