Amazon Fire Tablet 7in. I bought it literally just to read PDFs, and it was so slow that it was basically unusable. I tried switching out the launcher to something more minimal (Niagara launcher I think), and I figured out how to disable the ads that were all over the place. It helped a bit, but not enough to overcome the hardware and Fire OS. (I think I needed ADB for both of those fixes; I had to put in some real work to unfuck that tablet.) Plus the screen was too small for my pathetic human eyeballs.
Was it worth $30? At the time, yeah, because I literally couldn’t afford anything else, but I now have an $80 10in generic Android tablet that’s wildly faster.