I don't believe a signing solution is feasible. It's currently too complicated for even a lot of IT experts, and the amount of actors involved is too large to even move to a single unified solution.
Given that as of now authenticity can still be verified by experts, it's back to trusting journalistic outlets to properly verify news and sources.
Reminds me of tango and cash. Is this really true? Any sources for such verification techniques?
One might think that, given low enough resolution, any form of rasterized video or sampled audio can be convincingly faked even to experts, particularly once those with the faking technology fully assimilate such verification techniques so as to work around them.
Given that as of now authenticity can still be verified by experts, it's back to trusting journalistic outlets to properly verify news and sources.