I made MAIM, an open-source audio plugin that uses real MP3 encoders to distort the sound. I've also added knobs that let you "circuit bend" the encoders, changing parameters that would normally be inaccessible to the user to get strange glitchy sounds.
The plugin lets you switch between two MP3 encoders, since under the MP3 standard, the specifics of what to lose in MP3 lossy compression is left up to the encoder. The encoders are LAME, the gold standard for open-source MP3 encoders, and BladeEnc, an old open-source MP3 encoder that has a really bubbly sound and was fun to work with.
I'd love any feedback, and I'll be around to answer questions!
"The infinitely desirable sound of crappy mp3’s, broken cellphones, streaming videos, and much more."
I think Lossy approaches the same idea from a more artistic angle in contrast to MAIM which comes to a similar end from a more technical direction.
Coming from the 8-bit generation I find it interesting and refreshing that the younger generation seems to leave the harsh sound of the bit crusher behind and brings more sophistication into digital degradation. It's no surprise, of course, because low quality lossy compression is what they grew up with, in contrast to 4-bit 4 kHz bit banged crash, my generation would consider lo-fi.
Another plugin that is similar in spirit in the sense that it goes beyond simple downsampling to make things retro is AudioThing's Speakers. It has convolution samples from many old devices like the Gameboy or several old phones. I think it would be the perfect companion to listen to MP3 degraded sound with a speaker from your past.
[1] https://goodhertz.com/lossy/
[2] https://www.audiothing.net/effects/speakers/
I'm not affiliated with any of the companies mentioned. These are just plugins from my collection that came to my mind. Usually I do not post links to paid products at all, but I also think the VST plugin space is somewhat special in that it seems to allow many small companies to exist (maybe even prosper?), which is rare today, so I made an exception here.