Now that t/suki is using S3, I did some research into making it possible to upload audio files directly to the forum. As it turns out, it was pretty easy; the setting that controls it just checks the extension of the file.
The allowed extensions are now: jpg, jpeg, png, gif, heic, heif, webp, avif, mp3, ogg, m4a, wav, aac, flac, txt, pdf, doc, docx, and csv.
This should allow everyone to upload most pictures, audio, and documents to the forum!