I’m on Ubuntu 19.10 using Audacity 2.3.2. I installed Audacity from the Ubuntu Software Center.
I use Audacity to record vinyl LPs to FLAC. I’ve noticed that the program doesn’t play back the audio while it’s recording. Audacity for Windows does this. Why doesn’t Audacity for Linux?
Go to Recording Preferences and check on “Software playthrough of input”
See: https://manual.audacityteam.org/man/recording_preferences.html
WC
Yeah, I felt stupid when I was snooping around and found that in the FAQ documentation … here I troubled you to answer a question that the FAQ papers answered … sorry
Don’t worry - I had exactly the same problem a dozen years ago when I started transcribing my record collection to digital format - that’s what brought me to this forum in the first place, asking the very same question …
It’s only easy when you know how 
Peter.