in iOS is it possible to silence call ringing without using Do Not Disturb?

On my phone (iPhoneSE running iOS 12.x) I rarely ever receive any legitimate phone calls, but I get loads of spam.

I would like to silence all calls except for my one Emergency Contact, but without impacting any other notifications at all.

This means I can't use Do Not Disturb because it silences all notifications.

Is there any way to silence all phone rings except for one person, but without using DND mode or otherwise silencing notifications?

Immediately upon posting this question, I had a flash of insight as to a possible solution. Turns out it works perfectly! Here's what I did:

1. Add a "silent" ringtone to your phone (instructions at https://www.wikihow.tech/Set-a-Silent-Ringtone-on-an-iPhone or just Google "silent ringtone on iOS")
2. Set this silent tone as your default ringtone under Settings > Sounds
3. Enable a custom ringtone for all contacts that you actually do want the phone to ring for.

Note that the caller must not have their caller ID blocked for their custom ringtone to work.

Now your phone will only ring on calls from those specific contacts, and nobody else, all without using DND mode or disrupting any other notifications on your device. Nirvana!