A key issue is the fare class of different airlines are different.

A "P" fare on AC is economy but on UA is discount International business / domestic first class.

The fare class structures of airlines vary. In the case of codeshares, the marketing airline uses its fare structure but for mileage credit you need to know how that maps to the operating airline fare class. That is not easily obtain and best found by call the operating airline after ticketing (unfortunately).

Once armed with the operating airline fare class then use the link provided by ORDnHKG to determine earning. It is true that many airline operators are not providing miles for the deep discounted fares, presently UA is still 100% earning for the flights it operates.