I use the app Signal where I edit a photo with a blur markup option they provide and send it to myself, then save the photo & use it for anything outside of Signal.

MacRumors

How to Use Signal Messenger

Encrypted messaging app Signal features a face-blurring feature that automatically locates and blurs faces in images shared over the chat platform....

Gearbrain

Signal lets you blur faces in a photo with one tap

​The encrypted messaging app now has a feature to immediately blur faces you share within Signal automatically.