This one should work on 7.4 or higher: 
https://github.com/fabianfabian/nostr-media/releases/tag/0.3-alpha

only 2 php server requirements I haven’t been able to get rid of: ext-xml and ext-gmp. ext-xml shouldn’t be a problem, most WordPress hosting probably have this. ext-gmp I’m not sure, might be a problem for some hosts, it seems one of the schnorr libraries needs it.