Received wedding invitations back after rsvp deadline.

If you're close to them I would just reach out to them and let them know what happened. Ask them if they want you to send them again or if they're good with just getting the details elsewhere.

Since it's after the deadline, your venue probably needs a final head count very soon. I would forget the paper invites and just send them the link where they can RSVP online. Since you're close with them, I'm sure they'll understand and respond promptly.

If they've already RSVP'd I don't think it's necessary to send them out again.

I think it would be worth contacting them, saying the mail got returned, sharing a pic of the invite, and asking if they want you to resend the paper invite. Most people wouldn’t want it but some might want one to save! I think it is at least worth addressing with them bc personally I would start feeling a little weird if I didn’t get a physical invite