My Fairphone 3 has problems with the sound

[Incanus]

You can also start a hardware test to find out which part exactly doesn‘t work:

CHECKUP diagnosis on the FP3 – and its future

You can find this tool at the very buttom of developer options as Service Menu. (developer options need to be enabled first) I just want to add that the service test tool can also be accessed without developer options by dialling (in the phone app) * # * # 6 6 # * # * This is not available in /e/OS so far, as far as I can see. I think this basically closes the issue.