SIP ORIGINATE from a SIP Softphone


details on this are surprisingly scarce:
Is there a way in FreePBX, for SIP Clients (like softphones) to perform the Originate operation, other than AMI or WebRTC ?

(I know Originate through AMI works as I have been using the windows Dialer with appropriate module… requires the dialer to authenticate itself to the server; I also have used the UCP that uses WebRTC… Now I’d like to know, is there ANY way for the SIP Client to perform a SIP dialogue such that Originate would happen, rather than straight SIP session ?)
(I run in D&U mode and Originate is useful to instruct the softphone to dial a number, to be picked up on any other Device that User has; single-call-per-user usage is all I’m looking for at the moment)