I'm one of the ones running the adapter. Still no issues with it. Since I hadn't already performed the T21 recall (MB calls it something different), I didn't have to deal with "re-opening" it, however I can attest that it was still difficult to get the dealer to understand the problem. The new recall procedures unfortunately don't tell the dealer techs anything about the instrument cluster issues that are caused. The only way I got ahold of someone knowledgeable is I complained enough to the dealer and made enough calls to corporate customer service that the sprinter shop foreman called me directly and I didn't have to deal with the advisors or other front desk people. The foreman admitted that they don't really work on T1Ns anymore and hadn't done that recall any time recently, BUT he at least knew who to call. Since my dealer is a certified Sprinter dealer who sells volumes of new sprinters, they have a regional sprinter "REP" who covers multiple dealerships and is apparently a competent person connected to the factory and knew all about the new adapter/instrument cluster problems... Only once THAT person got involved did everything fall in to place.
So not really a trick, but maybe try pressing your dealer for their sprinter rep contact. Once you get in touch with someone who actually knows about the problem with these recalls, I would think they should re-open it. The issue is getting past all the front line customer service people that don't even know what a sprinter van is, let alone recall issues with them.
I did receive a survey from Daimler Vans after my service to which I wrote a stern complaint faulting them more than my actual dealer due to the lack of information they provide to their dealers regarding these recalls. I of course never heard anything back about whether is was read or not.