Ok, so what I would do is use a REGEX like I documented in MQTT 2.5 M1+ How to implement the equivalent to MQTT1 REGEX filters.
The difference will be instead of chaining this to another transform you will just set up the regec to match or not.
Then use the ON command field (I’m on my phone and can’t look up the right name) to send ON when ever any message is received.
The REGEX should filter out those messages that don’t apply to the device. The ON command will set the Switch Item lined to the Channel to get an ON command when ever a message that passes the regec is received.