MQTT Scene Disovery no longer working in 2022.2.2

I am using MQTT discovery extensively for my devices, and I built a couple of python scripts that integrate in my HA setup.
In my running HA version (2021.12.10) I am using the following data to my ‘discovery’ topic to make my scenes show up:

{"name": "Analog Clock", 
"uniq_id": "led_analog_clock", 
"avty_t": "domus/hassbian/availability/displaymode", 
"pl_avail": "online", 
"pl_not_avail": "offline", 
"cmd_t": "domus/hassbian/cmd/displaymode", 
"payload_on": "Analog Clock", 
"dev": {"name": "Domus Hassbian", 
"mdl": "Raspberry Pi 3 Model B Plus Rev 1.3", 
"mf": "Raspberry Pi", 
"ids": ["domus_hassbian"], 
"cns": [["ip", "xx.xx.xx.xx"], 
["mac", "xx:xx:xx:xx:xx:xx"]]}}`

(I blanked out the mac address and ip address)
And this works fine: it shows up as a scene, although not in the MQTT integration page.

However, I have a test setup running ‘bleeding edge’ HA version 2022.2.2, and there the scenes do show up, but they are all ‘unavailable’. I can make the scenes unavailable in my running setup if the payload on my ‘availability topic’ is ‘offline’, but in 2022.2.2 they remain so, even if the payload is ‘online’.

Am I missing something? I know there have been some changes in 2022.2.2 as regard to scenes, so maybe I am missing a field, but I have no clue.

All suggestions and help would be appreciated.

Ok, curiouser and curiouser: if I set the state manually to ‘available’ using the developer tools, after that it does respond to the ‘available’ and ‘unavailable’ states on the ‘availablility topic’…