Trying to come up with a workaround for Mastodon's brain-dead media behaviour. The only solution I've got currently is

if(your friend is using mastodon)
  do the wrong thing
else
  do the right thing

The issue is that half the metaverse does the wrong thing; which is basically stripping media from HTML content and adding it back as attachments. This is fine for OStatus and public networks but doesn't work with privacy enhanced services because the messages need to be signed, If you mangle multi-media messages to work on these primitive nets it breaks the signature, so you're basically stuffed. The messages will not federate because the service your friends are using is doing the wrong thing. If you don't mangle the posts to fit that network's policies, the media content will be stripped. If you do mangle the content, the message won't verify and will be discarded.

I do so wish that the people designing these protocols and systems would take a look at what the hell they're doing sometime. They're really screwing up everything for everybody.