It looks like the issue is not so much with netty, but with the upgrade of the hivemq bundle in the same PR. I have created an issue for it: #2346
It won’t be straightforward to solve this in an M4 install. The more likely workaround would be rolling back to M3 and insert the nikohomecontrol update in there. It may require quite a bit of effort to get it working though. I don’t have a version that was compiled before the hivemq upgrade. I would prefer to wait and see if we get anywhere with the issue resolution.