How to "trigger" an mqtt topic to read another topic

That’s the point. We don’t work here. We are volunteers. You need to start by helping yourself. Just asking for code written for you will not help. Show your code and tell us what you expect it to do and what doesn’t work and we’ll help. But you came in and said “write my code for me”.

I can do that (I charge for the service BTW). But you won’t learn anything out of it.

In the forum you need to start by helping yourself first and then we’ll help.

It starts from there: How to ask a good question / Help Us Help You

Also, my post above:

Hint: you can’t
You need to split your channels
One for the state topic
One for the command topic
Then create items for each
Create groups
Create a dummy switch
Create a rule and send a command to the command topic group (One line rule!)

Is everything you need. Work the steps, one by one. Figure it out. Understand it. Make mistakes. Get fustrated. Swear a bit. Try again. Search the forum. Try again. Read the docs. Read them again,. Have a coffee. Then when really stuck, POST WHAT YOU DID. and show what you tried. Then, we’ll help