Sadly, Google killed native SIP calling in Android 12. FFS!

It's relatively easy to get it set up again, although you'll need to install a separate app.

1. Sign up for a free Sipgate account. That will get you a UK phone number (+44), username, and password.
2. Install Linphone for Android (or via F-Droid)

Setting up Linphone should be straightforward. Enter your Sipgate username (a mix of letters and numbers) and password. The server is sipgate.co.uk. Finally, you must select UDP from the transport options.

And... that's it!

You can now call my SIP number from any phone +441234815259. It gets routed to Sipgate, which then notifies the app on my phone, which rings, and I can answer.

Sadly, because the native Android dialler doesn't support SIP - it's impossible to choose your SIP account when dialling. So you have to remember to open the Linphone app each time.

Why did Google remove SIP?

Because they're evil and they hate open standards which enable interoperability? Nah⁰.

Because mobile network operators are terrified of losing even the tiniest sliver of voice revenue? Nah⁰.

I suspect it was because close to zero people were using it. If you want to make a VoIP call, most people are using WhatsApp, Signal, Telegram, etc. I don't think I've ever seen someone advertising a SIP address in the wild.

It would be lovely if the big apps made even a vague attempt at interoperability. There's no technical reason why user@whatsapp.com can't place a call to user@telegram.org. But they're more interested in a "winner-takes-all" mentality rather than a collaborative effort which uplifts everyone.

Oh well.