If you are feeling adventurous, you could take another SD card, flash Armbian to it and install RoonBridge as outlined here.
The HDMI output will be available. I have not idea whether it will perform satisfactory (or at all) with ALSA/RoonBridge - but it’ll take you no more than half an hour to find out.
Do not overwrite the card with the SonicOrbiter OS that’s currently inside your SOSE: it contains all the niceties, patches and tweaks that @Jesus_Rodriguez and team have lovingly prepared.