The current UltraSync plugin is limited to systems which can be accessed locally. However there is a range of alarm systems (All sub-brands from Carrier) which are very commonly used that also make use of UltraSync. However they make use of UltraSync cloud (ultraconnect.com). Through the excellent blog post of Peter Csaba (Integrating the Hills Home Security System (Interlogix Ultrasync) with Home Assistant for Seamless Connectivity - IT DIY, Pentesting, Cyber Security) I have been able to login to my own system. However, integrating it into home assistant (which would require adjusting the ultrasync python library and the ultrasync plugin) is beyond my capabilities.
Having this plugin would make a lot of people happy, looking at how many people are trying to integrate Aritech, UTC, etc (all carrier sub-brands) alarm panels.