I think the answer here depends on how much trust you have for the different levels of tech in your phone. If you don't trust anything, the answer is install a

I think the answer here depends on how much trust you have for the different levels of tech in your phone. If you don't trust anything, the answer is install a hardware switch for the microphone or cover it with a sound blocker when you're not talking (just like if you don't trust your laptop's camera, put a piece of tape on it). If you trust the hardware, but not the OS, install something like Lineage to replace stock. If you trust the OS, but not the apps, uninstall any app that might have access to the microphone (especially "bad actor" apps like Facebook) and only use web versions.