For extra points, record it while in airplane mode, then delete the app. Snap now has no idea and cannot tattle.

IIRC, screen recording or screenshotting will bubble an alert to the other party about what you've done, unless you disconnect from the network or some other shenanigans.

Of course, taking a regular old picture of the screen of a DRM'd device is still a thing in your own private home. DRM goes only so far, though deterrence does help to some extent I'll admit. Question is if we're willing to accept DRM'd devices following us around all day long so that we can have nudes via a not-e2ee messenger with slightly less risk of the other person sharing it.

About some other shenanigans if you really care about recording the screen you can use another phone or a camera, possibly on a tripod to keep it steady and the distance constant. That's lower quality than a screenshot but it's basically undetectable.

And how about running in a VM on a desktop? Does Snapchat allow that?

on my Pixel screen recording doesn't notify the other user.

Interestingly, my GF asked me a few hours before if I knew (I did in fact not) that users get a notification when you screenshot their stories from Instagram.