Sorry if I wasn’t clear, I added a completely separate manual alarm (with no physical device) called ‘HA Alarm’ through HA and then pointed the alarm card at that entity. So I have 2 alarms in HA (I did say it was a bodge!)
I then set up several automations to change the state of each alarm to match the state of the other one. E.g. If Yale alarm set to disarmed set HA Alarm to disarmed, or if HA Alarm set to disarmed, set Yale alarm to disarmed. You need to do this for each state (armed_away, armed_home, disarmed) both ways - so quite a few automations.
The HA alarm works with the Alarm Panel card and shows a key pad, so I add that one to my dashboards, and when I arm/disarm it, the Yale one arms/disarms. IT works, but it’s quite a bit of effort to initially set up and is far from an ideal solution!