Is it possible to use archive.org or something similar in place or in addition to the builtin archiving?

That’s actually one of the features, you can enable it from the settings to send the link to archive.org for a snapshot.

No prob!

Collaboration, making your collections public, better organization, self-hostedness (idk if that’s a word), better UI and so on…

Like this: https://cloud.linkwarden.app/public/collections/118

Thanks!