Hi folks, I have posted this on Reddit under /r/Mikrotik but I'm also posting it here with slightly different language.
However I will say that I am seriously miffed at Mikrotik for the way that Netinstall actually works and why it's broken on Windows 11. Put simply, the package transfer mechanism in Netinstall uses all broadcast traffic - including the package transfer itself. Putting aside the utter ridiculousness of using broadcast storms to transfer data under ANY circumstances, the system completely fails on Windows 11 because the initial "offer" broadcast packet is send via UDP using Source port 5000 and Destination port 5000, which is silently blocked on Windows 11 regardless of Firewall status, network interfaces enabled or any other setting I can (so far) find.
Mikrotik, this is a complete box of frogs and you need to fix this. I understand why you have used broadcasts, and it's so that many (hundreds even) of routers could all receive the same package file at once. I suppose you may even do this in your factory as the means of flashing ROS to boards before they are shipped.
But honestly, it is wrong to require a broadcast-storm method of file transfer in Netinstall. It should use unicast methods, and there is no reason this is not possible because the first stage of Netinstall uses BOOTP and TFTP unicast already.