Audacity can seem to be recording from both sides when what it’s really doing is recording one thing very well and faulty echo cancellation of the other. A variation of this is a complaint that the far side is gargly or bubbly and how do they clear it up. You usually don’t. It’s a cousin problem of compression distortion. There’s pieces of sound missing and non-recoverable
Every so often, someone will discover that they can record, for example, Skype perfectly and create a production around it. Sometimes they post notes how easy it is and we get a flurry of postings how hard it is. Those successful people are celebrity unicorns and what they’re doing is very unusual.
I’m guessing they’re taking advantage of an anomaly or defective service in their computer. If they change or upgrade to a different machine, it will stop working.
In general, we don’t get complaints about people using purpose-built recording software (there have been problems with those, too) and no complaints from people using the two computer and mixer technique.
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If the two conversations are relatively clean and not too far apart, you can try LevelSpeech
https://forum.audacityteam.org/t/improved-leveling-for-speech/33258/27
or Chris’s Compressor.
https://theaudacitytopodcast.com/chriss-dynamic-compressor-plugin-for-audacity/
Koz