I see no community responses so I am sharing what I found: https://www.amazon.com/RecorderGear-PR200-Bluetooth-Recording-Recorder/dp/B01CIATFB4?tag=p00935-20&ascsubtag=07A2ftwHJ8B2X9Xz0rVWHsA. I am all ears if you are using something similar of „better” known vendor. Many thanks!

There's no way from the phone. The apps are all crap and only get your side of the conversation clearly. If you can root the phone, which isn't available yet, then you can load custom root software that allows this natively. Otherwise your best bet is a bluetooth device the phone casts to during a call. Here's one such device from a quick google search, but there are tons of options. Find what would suit you best. https://www.amazon.com/RecorderGear-PR200-Bluetooth-Recording-Recorder/dp/B01CIATFB4

The advantage with an external device is no fuss with the phone and other phones over the years. Phone gets upgraded later, but this device is still here for your use. Just my two cents, good luck!