Sourcehut was mentioned:
 
sourcehut
~ft/hj264
hj264
H.264 encoder for Plan 9.
https://git.sr.ht/~ft/hj264

Orca, neindaw, and netsurf were mentioned:
orca - ORCΛ for Plan 9.
neindaw - DAW as a file system (use with orca).
netsurf - APE port with Plan 9 native frontend. Works.

Free Carrots #3: Additional Software
http://helpful.cat-v.org/Blog/2021/01/27/0/

There is a wiki playground tutorial that mentions IMAP.

Receiving and sending emails with 9front
https://wiki.sdf.org/doku.php?id=playground:email_with_9front

AUDIO(1)
http://man.9front.org/1/audio

NAME
     mp3dec, mp3enc, oggdec, oggenc, flacdec, flacenc, sundec,
     wavdec, pcmconv, mixfs - decode and encode audio files

DD(1)
http://man.9front.org/1/dd

NAME
     dd - convert and copy a file

MUG(1)
http://man.9front.org/1/mug

NAME
     mug - convert an image to a face icon