My old-ass phone is already crying about memory, and downloading the app from Github is still a pain, so I'm going to wait. Seriously though, is there anything stopping someone from straight up uploading child porn? Will Amethyst users just be randomly downloading it by default?

It's not by default I said it can be done by default, servers can scam for csam like nostrbuild is doing and I don't think anyone will go to run their own server to upload such things.