......snip

In pavucontrol (audio mixer), first check the configuration tab, to see
if the Built-in Audio is set up correctly. "Analog stereo duplex" is
probably right.
Then, on the "Input devices" tab, at the bottom set it to show
"Hardware Input Devices", then check that the Port is set to the
correct port. For me, "Line In" shows correctly if something is plugged
in or not. Make also sure the gain is set to 100%.
That said, I sometimes have problems recording LineIn with Audacity,
even though all seems OK. have not yet determined what the cause is.

......snip

Audacity can record audio, it uses an internal 32 bit floating point
format by default, which is the best IMHO.
It exports in a number of formats, for FLAC select the audio you want
to export, choose File->export_select_audio, choose the flac format in
the  drop-down box near the right bottom. Change the file extension in
.flac. I use Audacity multiple times per week.

I just plugged in my UCA202, and the system (Mint 20.2 XFCE)
immediately recognized it. It shows up in the audio mixer (pavucontrol)
as an extra input device and extra output device, both as "PCM2902
Audio Codec Analog Stereo".