Having tried every piece of Boldbeast-advice without any result, it seems that I'm finally able to record calls with Boldbeast again. After I turned off everything Bixby and the Samsung recorder app I was able to record both my own voice and the voice of the person I talked to, using Record mode 12. It doesn't matter if I enable Tune Audio Effect. Tune Samsung2 is enabled, but I haven't tried it with this feature disabled.
However: The voice of the person on the other end is remarkably weaker than my voice in the recording. Can anyone recommend any settings to increase the volume on the other side?
And: It seems to record every call even if I opt to only record calls from numbers that aren't in my contact list. Is this an error, or have I forgotten to do someting?