Understood !
Just a thought … on the screen turns off issue, are you aware of the proximity sensor? The screen is expected to go off as you put the phone to you ear, and to come back on as you take the phone away from your ear to look at it. This can be tested with the phone out of any case, and you move your hand in the region of the sensor.
Regarding logcat it might be worth reviewing this page. https://doc.e.foundation/support-topics/create-a-log.html. There is a logcat facility built into /e/OS but I do not see an entry level intro to it in https://doc.e.foundation/support-topics.
The speaker issue looks hard to fix, but it might be a good idea to to open another thread on the subject of speakers and check out if others users here are affected. The logcat will probably be less useful in this case.
You can start a new topic (and avoid too many duplicated words) like this
Edit, I notice that you tested other dialers Murena: best dialer – did this have any impact on this issue?
Further edit, I see this issue (with a similar one linked within) in the Teracube forum.