If you are looking for a form of rotation and flipping that rotates the actual video, rather than relying on CSS to achieve it, you can check out the sender-side &effects options.
https://vdo.ninja/beta/?effects=-1, which will flip the video
https://vdo.ninja/beta/?effects=-2, which will flip and mirror the video
https://vdo.ninja/beta/?effects=2, which will mirror the video
Effects however may increase CPU/GPU usage, and could cause frame rate instability, especially if the browser tab is not in active focus.