Ringtone volume issue on my iPhone 12

Try using a different ringtone to see if it appears any louder. Check to make sure the speaker at the bottom of the phone is clear and there is nothing blocking the speaker at the top of the phone.

You can also test the volume of the ringer by going to Settings>Sounds & Haptics. Under Ringtones and Alert, take the slider all the way to the right and release. You should hear the ringtone that you have selected at its highest level. Does it sound different from when you receive a phone call?

Hello!

Go to: Settings > Face ID & Passcode > Attention Aware Features, and turn it off. See if that helps.

I understand what you asked. Did you try the steps that I provided?

Good catch. I've gotten so used to that not working lately that I forget to mention it anymore.

Not so much a “catch” as a mere suggestion. You’re good. 🙂