Configure siproxd for linphone thru wireguard on 18.06.5

wg0=wireguard vpn tunnel address
openwrt 18.06.5 router address is wg vpn address is

goal is to have 2 way phone communicate using only wg vpn addresses from
linphone client-A [local ip] (remote over wan)
linphone client-B [local ip] (lan and behind openwrt)

client-A can ping client-B and vice-versa.
However within linphone it also makes use of the local IPs which we believe are
a problem (shown within linphone as SIP resulting ip 192.168.) with symptoms of NOT hearing audio on both ends and are trying to resolve by using siproxd,

What would be a configuration with siproxd that would cause linphone to use only our wg0 vpn respective addresses i.e. 172.21.120.x where x is either 3 or 15 ???

Do your linphone clients support ice? When using ice the clients should add all local IP addresses as candidates in the sdp which then will be tried by the remote end.