The problem I was reporting was showing up in Windows as well as on Android and Xbox One. Otherwise, I would have assumed it was something happening on the Windows side of things. While I thought it was most likely your docker image, it certainly could be something I inadvertently changed on my router. Just to be safe, I went ahead and added a vanilla installation of BDS on my Ubuntu VM running on unRAID and sure enough, it worked the way it did before and shows up in Windows, Android and Xbox just fine:
So now I'm left with the question: why is BDS showing up on my LAN when running from my Ubuntu VM but not when running on your docker? I do have my VM running it's own virtual network adapter and so I tried the same thing with your docker image (latest), but no dice. No combination of networking seems to affect whether or not it shows up in Windows, Android or Xbox, though I'm decidedly a docker novice. If you -- or anyone else -- knows how this is being broadcast in BDS, perhaps we can figure out what specific network configuration I'd need to get it working for me. It seems like I'm not the only one experiencing this issue.