Hallo 'zammen,
This is a bit belated. Thanks everyone for the opportunity to present at the last SwiNOG meeting about Manufacturer Usage Descriptions. As a status, I've landed code for dhcpcd so that if you happen to be building a small Raspberry Pi-like device it's a simple tweak to add a MUD URL. In addition, if you would like to build a MUD file description, you can go to https://www.ofcourseimright.com/mudmaker and create the appropriate file to point to. In addition, if you want to debug, I've a pull request now pending for tcpdump.
The same is more or less case for the PKIX / 802.1ar option. We have an assignment now from IANA and it is possible to add the appropriate extension using Openssl. I'm working on dropping some code into wireshark for debugging, but that is taking just a bit longer.
Questions? Feel free to drop me a line.
Eliot