pavucontrol, activate UR22mk2 or your USB-Headset-Microsphone as Input, activate USB-Headset as Output, then:
$ pactl load-module module-loopback latency_msec=20
pavucontrol, see tab "Recording ".
There the loopback options appear.
Here also You can pause the loopback, alternatively:
$ pactl unload-module module-loopback
Please note: Once an input source is used for loopback, you can no longer use it as input in Audacity, since Audacity needs this exclusively (Audacity error
Error opening recording device. Error Code: -9985 Device unavailable
would appear then).
On the other side, OBS is able to record from the input and monitor it at the same time.