Try this https://drive.google.com/file/d/1t9PpvmhIFyBhiVu4N3ufkMlzhU-N9BwN/view and the .bat file https://drive.google.com/file/d/1CyHreqaJQOfb7M-ohaNRyEir77nan88r/view.
I got all this info from this Reddit thread -> https://www.reddit.com/r/halomods/comments/n6hv50/how_to_downgrade_mcc_so_you_can_play_your_old/
I have a feeling we're SOL... its now 2024 & MCC hasn't been updated for years. At least I got to play the CE one, but that only has set my desire to play the other Ruby mods more. It's a shame :(
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* Choose the September 22 versions of Halo MCC: Base and Halo 3: Campaign
* Install the mod over the top of your downgraded version
Voilla, it works.
I got all this info from this Reddit thread -> https://www.reddit.com/r/halomods/comments/n6hv50/how_to_downgrade_mcc_so_you_can_play_your_old/
Good luck!