See also: Black Hole Vision for iOS from Vanderbilt University. https://apps.apple.com/us/app/black-hole-vision/id6737292448

Yes, linked in the readme! They simulate light bending, but ignore time delay effects.

I think the earliest of these black-hole-camera renderings is https://dominic-chang.com/bhi-filter/ though (also linked in readme) – a direct inspiration for the camera mode in my app!