Greetings from SensorFu and thanks for a good question! Sending DNS query via broadcast is a hack to escape from isolated environments and it takes advantage of operating system IP-stack's shortcomings. Since this is probably not conforming to any specifications anything could happen.
I'd say return channel might work and it depends on the device used to exfiltrate out. In case of proper DNS server like Active Directory mentioned in the article it's likely that it could work. But we have not yet done testing.
We have also seen devices that are not DNS servers and still just forward broadcast packets from one network interface to another. In such case the return channel might not be possible.
The minimal effort included hours of studying electrical engineering and radio technology at university including all the math and physics needed. Studying for amateur radio license. And after founding this issue delving deep into radio interference literature and datasheets of various components. Then setting up a test environment to replicate the issue and do tests trying to eliminate the interference. After a success write a blog post describing the solution in short and hopefully interesting way.
The issue was confirmed with two separate MagSafe chargers and three or four separate AC/DC chargers. The lab test in the post was done using laboratory DC power supply powering a DC to USB converter.
Also if the interference didn't come from the disc side of charger then the issue wouldn't be resolved with ferrite bead on that end. If the issue was on the USB connector side then the bead should be placed there.
You can be using a device and it might not harm you personally, but it could harm anyone around you using these frequencies. This includes airplanes and ground control, and boats. Your device's interference could cause problems or even life threatening dangerous situations. That's why it's illegal in many countries to cause too much radio interference (there's always some).
RouterOS by default doesn't have container support. It's a separate package which has to be installed on the system. And it is still in testing / beta phase.