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I've tried two apps to record calls that work quite well on other Androids - both called Call Recorder. None of the settings could prompt it record a thing.
The help page of one lists ZTE Blade as incompatible, though I don't know if that only refers to the old Orange San Francisco. I believe the SU6 is a very close cousin of the Blade 6 Plus.
The lack of this feature is a bit of a disaster in an otherwise near-perfect device. I need to record some stuff for legal reasons and I'm forced to go sim-swopping back to my old grot-fone!
Let me know if you get anything to function.
This one works great -
Yes it is possible. There are many call recorders for these purposes, so it is possible to install spyware applications which has a call recorder.
I just wanted to point out that the application that @vondes has linked to is a third-party app that isn't from Google Play/iTunes stores directly.
I'd personally recommend only downloading apps from official stores. If you do decide to download a non-verified application, you do so at your own risk and this may cause issues with your phone.