How to permanently allow ony one microphone to provide input / how to block microphones?

I use Ubuntu 20.04 LTS. I have two microphones:

• One from the camera,
• The second one within my headphones connected through mini Jack.

I don’t ever want to use the first one from the camera. Unfortunately, even if I set proper input in system settings / ALSA, sometimes it is used by some applications. Is there any possibility to permanently disable it, so that I cannot accidentally start using it during for example Zoom meeting?