How about if when the app's data is fully locked down, people start recording their screens and OCRing them? Incentivize it somehow. That way at least content that the participating users viewed would be indexed. Then you get back to trying to block people from recording their own screen with software, and after that hardware[1]. Never ending cat and mouse game.
1: https://pallycon.com/blog/choose-your-weapon-to-fight-screen... (see "Screen recording using camera")
And outside the technical level, discord also has the legal way. They can try to shut down your service, remove your code from public space and make you sink more time and money in an uphill-battle.
This is the same battle people are fighting against all walled gardens. And so far the gardens usually win. So someone taking on that fight, should be aware of this.
I guess if a big name like Google would ask them and ensures that privacy is preserved, they might cooperate to some degree.