It occurs to me this is the sort of problem the satellite internet constellations could help solve.
The issue of authenticity is getting some third party to attest that video happened at a particular date and time - at least part of that solution could be getting the various low orbit constellations to provide a simple timestamping service for hashes. Since the orbits are known, and position can be triangulated, any 3 satellites signatures would at least prove you transmitted a particular hash for attestation at a given date and time.
This obviously doesn't help with someone traveling there and sending junk, or using local repeaters to send junk, but it ups the difficulty level a notch.
That's the idea of using the low orbit constellations - obviously this doesn't work if you're just passively recording a broadcast, it has to be 2-way - which rules out anything not designed for that.
But low-orbit satellite internet is designed for 2 way communications, and probably already has the equipment on board to calculate checksums (or at the very least is a sufficiently trusted third party).
So we develop a protocol we can run on miniaturizable boxes which can be served point-to-point with the constellation members to at least prove transmission origin providence.
In this scheme they would be controlled by a central party, as effectively we're talking about Starlink and SpaceX. Or maybe one of the legacy satellite internet providers.
Assuming that though, you send a hash of your content up to the system, which geolocates it (based on physical reception), adds a timestamp and geolocation into the metadata, and returns the signed information, using the central party's key.
You also could run a similar method on cellular networks by using towers as the signing node and the telecom as the centralized entity.
Because realistically, it's not Byzantine Generals. What you want is (a) timestamp verified by a trusted party, (b) geolocation verified by a trusted party, (c) content hashed/signed to prevent subsequent modification, (d) prevention of replay forging of (a) or (b), & (e) most of the infrastructure not physically accessible by users (e.g. signing chip embedded in a camera).
The issue of authenticity is getting some third party to attest that video happened at a particular date and time - at least part of that solution could be getting the various low orbit constellations to provide a simple timestamping service for hashes. Since the orbits are known, and position can be triangulated, any 3 satellites signatures would at least prove you transmitted a particular hash for attestation at a given date and time.
This obviously doesn't help with someone traveling there and sending junk, or using local repeaters to send junk, but it ups the difficulty level a notch.