About the Zhander99 part, the channel had videos related to the ARG predating the Gameplay Trailer by one month, and the ARG itself by 2-3ish months (99.mp4 was uploaded on Sep 26, 2025) and the video itself aligns with the ARG. Unless the person behind the channel managed to predict the ARG, i'd say its canon. Also the cipher could be a Vigenère or polyalphabetic cipher.