i just did fresh install of mx linux 19.3 and audacity 2.3.2. turntable connected to preamp USB PhonoPlus by Artcessories. USB out from that to Linux box. In pulseaudio volume gui, i can see input occurring "alsa plug-in (audacity) Alsa Capture from “PCM2902 AUDIO COdec Analog Stereo” but I can’t get audio out of speakers. I have software playthru off.
Do you mean while recording, or when you play from Audacity, or no sound playing anything from any app?
When you click “start monitoring” do you see the LEDs jumping? You might have to put software play through “on” instead of off; otherwise you will not hear the track you are recording coming through the headphone jack…