Using OpenCore, I was curious to see if it would run on a 2015 MacBook Pro. Using an external Samsung i7 500GB . The current OpenCore version is 13.3.1. EVERYTHING works! iCloud, Photos, Messages, Music library all synced with iCloud. Stage Manager works without a hitch. I have found no performance drawbacks that would justify Apple not making it available for this model. Obviously the 2015 isn't my daily driver, but I will probably use it more often than my M1 MacBook Air. I mainly wanted to try this as I was pissed that Apple doesn't support iCloud on Monterey.