Comment by _JamesA_

Acrobits Softphone[1] and Groundwire[2] support iOS push notifications. I have found they work much better than Bria[3].

[1]: https://apps.apple.com/us/app/acrobits-softphone/id314192799

[2]: https://apps.apple.com/us/app/acrobits-groundwire/id37850308...

[3]: https://apps.apple.com/us/app/bria-mobile-voip-softphone/id1...