Important: this wiring diagram does not describe the Mazda 3 type BP (2019), it's for the older model BM/BN (-2019). Just as info for all who are searching for wiring diagram for the actual BP.
Important note: these instructions do not apply to the Mazda 3 type BP (2019-), which you can see in the picture above, but to its predecessor, the BM/BN.