Modify your ~/.asoundrc as shown below. This will destroy the ability of your user account to make sound without the jack sound server running but gives capability to pipe sound to idjc from about half of all alsa applications. The rest fail due to overfilling the buffer or something like that. Linphone generates real time audio data so it's probably okay.

Ideally make a special user account for when you use IDJC. I suggest giving this account at least read access to the media files in your regular account.

pcm.idjcvoip {
type plug
slave.pcm {
type jack
playback_ports {
0 idjc-mx:voip_in_l
1 idjc-mx:voip_in_r
capture_ports {
0 idjc-mx:voip_out_l
1 idjc-mx:voip_out_r

!default idjcvoip