Yes, these are quite old. I've written a GLSL shader that acts as a simple ISP capable of real-time video processing and described it in detail here: https://source.puri.sm/-/snippets/1223

It's still pretty basic compared to hardware accelerated state-of-the-art, but I think it produces decent output in a fraction of a second on the device itself, which isn't exactly a powerhouse: https://social.librem.one/@dos/115091388610379313

Before that, I had an app for offline processing that was calling darktable-cli on the phone, but it took about 30 seconds to process a single photo with it :)