1. Upgrading to MK2.5S is a must

⬢In order to get the MMU2S running properly and without any issues, you MUST upgrade to the MK2.5S.

⬢Why? Well the firmware is expecting filament IR-sensor, Noctua fan, new P.I.N.D.A. sensor and other improvements, which aren't present on the MK2/S.