→Softphones: Voipfone Softphone on Android doesn't make SIP URI calls to numeric usernames - it calls the number directly.
* Linphone 4.0.1 (Android)
* Twinkle (Linux) - although currently (Dec 2018) there's a problem with SRV records when using systemd-resolved (on Ubuntu and Debian at least)
* Voipfone Softphone (Android) deserves a mention. It needs an account with voipfone.co.uk, but you can signup and try for free. Their softphone app
just works out of the box for calling SIP URIs.