DownSights covers the entire Call of Duty Black Ops: Cold War easter egg that was carried out online and in game, in Call of Duty: Warzone. They cover everything from start to finish on how the easter egg was solved, including the solutions for all the ciphers that are part of the easter egg.
Source: N4G PC How To Solve The Ciphers (Call of Duty: Black Ops Cold War – Easter Egg Guide)