Trouble recording on my laptop

I have a 17" LG Gram laptop on which I run Xubuntu 20.04 with Audacity
2.3.3 installed.

I also run Xubuntu (20.04 with Audacity 2.3.3) on my desktop.  I have
little or no trouble with the recordings o the desktop.

On the laptop, the only mechanism I have found that works to record
something in Audacity insists on using the laptop's built-in
microphone, which is fine under most circumstances.

However, I would like to record the line input coming from, say, an
audio I'm playing in my browser or something else I may want to record
but not have to play it on the speakers so the built in mike can
"hear" it.  I don't see how to do this.

On my desktop, this is fairly simple - I just use the "default" mike
that's setup on installation.  I'm not absolutely sure, but I also
think there are no other special flags set to allow this.

On the LG, this is not the case - no matter what I do, I can't get
Audacity to record from the line input - ever.

Is there something about laptops that makes this harder that I
(clearly) don't understand?  I had similar problems with an older HP
laptop, also running Xubuntu (16.04 and 18.04), but I found a way
around them.  The LG refuses to allow this no matter what.

For the record, LG does not acknowledge that I can even run anything
other than the original installed Windows 10.  As a long time Linux
user (and engineer), I found a simple enough way to make that work as
a dual boot.

Is this an Audacity bug I should report (and, if so, what other info
do you need)?

If not, can anyone tell me what I'm doing wrong here?

I've been an Audacity user (and fan) for years, and I've read the docs
several times, and looked on the web for ansers.  I found some before
which helped me solve the HP problem, but none of that works on the
LG.

Advise?  Comments?  References?

Most appreciated.

Mark Richter, Senior Software Enginer
http://www.linkedin.com/in/markrichter1
Registered Linux User #472807 http://counter.li.org/
FSF Member #12694 http://www.fsf.org