I wondered, Browsers work really well, are already there anyways, have all the GPU stuff etc already dealt with. They also have portal support so Wayland works great.
It could use the Browsers screencast ability on all platforms, and run with Javascript and WASM.
The stuff could be installed in a local Podman container and thus also work natively on Linux.
Do you know an app that does this, client-side?
Thanks to the actually helpful people:
screenity, GPLv3, has some nice features
recordscreen.io some random webservice, the recording is supposedly done in the browser. Proprietary.
Fair points. A video recorder for me doesnt need internet access while a browser obviously has it. A browser needs that for me as I use it for video calls, even though it is a bit strange to do this.
But thats it, browsers are multimedia platforms today and using another tool additionally to that doesnt change anything.