@pluralistic
The solution to a lot of this might be open hardware. A garage door opener isn't that fucking complex. It should be possible to build a prototype with a micro-controller and a couple of relays. Unless Chamberlain wants to make an argument that looking at the leads of a motor are proprietary, which would be absurd (and probably unsuccessful). Once that's done, we have the tools to create an open hardware controller on a custom PCB at a reasonable cost. Then one rips out the proprietary controller, drops in a replacement, and carries on. I seem to recall a group that was working on this with the infamous John Deere farm equipment. No right to repair? Well then, how about a right to replace?
Edit: fixed weird duplication of the text!