As
@Billie Nelson said, not all non-DJI batteries are substandard. I have 3 PowerExtra and one FlyHi battery. Two of my PowerExtra batteries have over 150 charge cycles on them. They outlasted my original DJI battery which I retired long ago due to swelling. The only difference is that the LED lights are not as bright as the DJI battery. I will likely be retiring my two oldest PowerExtra batteries soon and replacing them with another new PowerExtra.
I just retired two of my DJI Spark batteries due to swelling. I sure wish there was third party batteries available for it as the price of Spark batteries has shot up greatly in the last year as they become harder to find.
Chris