Anna's Archive, Libgen, Mobilism, IRC (I use a self-hosted service called OpenBooks for this). I use Calibre for metadata sorting, plug Kindle in and move books that way and keep it on airplane mode.
Also, new Kindle jailbreak for <= 5.16.2.1.1 if anyone's interested. Managed to get KoReader on my 10th Gen Basic.
I didn't have ads either but being able to use KoReader is a good enough motivation for me.
Overall there are a lot of steps to it, if you're comfortable with your current setup it's not worth the hassle/time.