Apple seeds do contain cyanide, and they can be dangerous. Key word here is CAN.
Approx 1 gram of apple seeds contains 0.6 milligrams of cyanide. So while it depends on ur weight, height, etc, consuming about 200 seeds at once could prove to be lethal. To get that much, you’d have to eat around 20-25 apples. Which would be hard to do unless you just REALLY love apples.
So while unknowingly eating a few seeds won’t kill you, it’s probably best to avoid them.
And the seed shell coating is probably too strong for your stomach to digest, meaning you would need to eat 25 apples within a 1-5 minute time frame but also make sure to chew up every seed so that their surface area was increased and their internals were available to be absorbed.
Frankly, apple seeds are only dangerous if you get shot in the eye or ear with one.
I cant give any scientific comment on this one, but at one point i was eating a medium sized apple every single day for an entire school year. I ate everything but the stem, and only spit out the seeds sometimes. 5 years later im still fine haha, but it seems like the general consensus from other comments is that you would need to consume a lot of seeds in a shorter time frame for it to have a potentially fatal effect