I don't have an answer to your actual question other than self-hosting. But, I doubt you'd ever get a "firehose of trash" on your main feed. Mainly because the trashy instances aren't that populous, so I doubt their posts would be active or hot enough to float to the top. But I could be wrong.
You could always go directly to the instance you want to read and lurk. Unless you make an account you won't be able to comment, but you'll be able to get your firehose of trash
Edit: Just be mindful of how much you consume, you'd be surprised how easily hate can invade your mind. To this day I still have to self-censor every now and then thanks to the hateful rhetoric I grew up around, even though I'm long past it