Out of curiosity, I tried to get Linphone-Desktop to function properly in desktop mode on my Fairphone 4 channel 24.04/daily.
Linphone-Desktop exists in many versions:
AppImage(s) 4.x.y to 6.x.y, alphas, betas, nightly
qt5 version(s) 5.x.y
DEB version(s) 5.x.y
qt6 version(s) 6.x.y
DEB version(s) 6.x.y
The ugliest install is probably the qt6 version straight from the main branch available on gitlab or github. I went for the main branch version in the trial to see if it would work.
Compiling Linphone-Desktop is probably worth an essay by itself, but it is pretty straight forward to set CMAKE options where neccessary. Packaging Linphone-Desktop into an installable DEB is probably worth another essay. It is also possible to unpack the AppImage version into a Libertine container somewhere like /opt/linphone and adjust LD_LIBRARY_PATH variable to give the executable a chance to find all libraries inside /opt.
When launching from command line, there was a complaint about a missing qt6 module named Suru, but I kept re-launching the same command 3-5 times until Linphone-Desktop launched anyway without Suru module. The successfull Libertine container noble launch command was entered five times like this:
QT_USE_PHYSICAL_DPI=1 QT_SCALE_FACTOR=0.8 GDK_BACKEND=x11 LD_LIBRARY_PATH="/opt/Qt6.10.2/lib:/opt/linphone/lib:$LD_LIBRARY_PATH" /opt/linphone/bin/linphone -V
Remark: Sometimes Linphone-Desktop launches at first or third attempt. Linphone-Desktop should compile with any qt bigger or equal to version 6.10.0 (I used qt6.10.2). The initial launch showed such a tiny text in desktop mode that it was not readable at all. Some tinkering with variables in command line launch made the text bigger and the app more useful.
Testing
Linphone-Desktop offers encryption of different types, such as PostQuantum ZRTP, which worked.
Several different sound card options appeared in the settings, of which the Droid soundcard worked.
Tested encrypted chat message delivery which worked.
Tested encrypted voice call (SIPS-protocol) with opus codec which worked.
Video camera did not work. Only static picture could be selected in the settings, which worked and was shown.
Observations
Earlier versions of Ubuntu Touch has a native Linphone, which I think would be nice to have in noble as well. It may not offer the advanced encryption available in version 6, but still good enough performance compatible with other SIP-softphones.
Ubuntu Touch noble (24.04) does not have a native Linphone or any other SIP-softphone as far as I am aware.
On devices that do not meet operator's VoLTE requirements, SIP-softphones is an alternative for calls. Signal-Desktop is another voice calling option.
I was not expecting Linphone-Desktop version 6 to work on Ubuntu Touch noble as well as it performed. Sound quality was good and chats were delivered as expected. Some icons were a bit too large, but visible.
Wired external display functionality (USB3 display out) seems to be a more than neccessary feature of a device that for the moment requires desktop mode to show windows which are too large for a mobile screen dimension.
It should in theory be possible to port the Android version of Linphone to Ubuntu Touch, given that Linphone-Desktop works out of the box more or less. Maybe the developers of Linphone would be interested in helping out with that.
