It appears to not have been enabled by default on my instance of uBlock; it seems a specific filter list is used to implement this [0]; that filter was un-checked; I have no idea why. The contents of that filter list are here [1]; notice that there are exceptions for certain services, so be sure to read through the exceptions before enabling it.

[0] Filter Lists -> Privacy -> Block Outsider Intrusion into Lan

[1] <https://github.com/uBlockOrigin/uAssets/blob/master/filters/...>