On Samsung Android phones there is a Samsung app that isn't installed by default that allows to individually manage volume/mute per app called SoundAssistant (and few more neat customizations for audio/audio controls).

I don't think many people know about it, it's made by Good Lock Labs which is basically a group of Samsung devs making advanced customization apps: https://galaxystore.samsung.com/detail/com.samsung.android.s...

You access the features from the OS volume control once installed, there's a "..." button.

Always wondered if that also works on non-Samsung phones, but it's quite useful to forever mute an app.