Google has deliberately prevented call recorders from working in the latest Android version. They admit it here: https://support.google.com/android/thread/27896902?hl=en&msgid=27921755
I think that is bad. Recording phone calls is useful for at least two purposes:
1) As an enhancement of your own memory
2) As a tool to keep other people responsible when they can be held accountable for what they have said to you.
One reason email is attractive is that each participant has a "recording" of the conversations one has particapated in. The same should be possible for phone calls.
What is the best smartphone operating system which hasn't got that limitation created by Android?
I prefer something which is relatively open.