You can write a Kwin script and connect to the windowActivated function. Unfortunately you can't run arbitrary command from Kwin script, but as suggested in the comment you can use DBus to workaround that.

workspace.windowActivated.connect(function(client) {
    if (client != null && client.caption == "name") {
        callDBus(...); // call your DBus function which call ddcutil
    }
})

Just an example, you will have to do some trial and error yourself!

what's the exact prompt?

I'm using Tailscale Status Gnome extension which works pretty well. But good to see alternatives that is not tied to specific DE.

GitLab don't have the monetary incentive to implement federation. Most of their revenue is coming from big companies which are mostly using private GitLab instance and won't want their projects federated.

That being said, hope this changes can get merge as somebody already done the dirty work for them. The beauty of open source.