One thing that I would assume, though, is that any Honda dealer should be able to service your car.
Alas no! one dealer said she had never heard of Clarity, and after touching base with her manager she told my wife that Clarity was sold only in California. If so, Toyota (RAV4 plug-in 2021) and Kia (Sorento plug-in 2022) and perhaps others will be eating Honda's lunch in the East Coast. Not to mention Carmax and Carvana who are selling used Claritys anywhere you like. Honda and Clarity deserve better.
Any Honda dealer can service Clarity, it uses the same i-MMD hybrid system as the Accord, CR-V and Insight which dealers are already used to, the only real difference is the larger battery, larger electric motor, the battery cooler and the charger. Even if it's their first Clarity they have plenty of resources from Honda, no different than when any new model arrives and they get their first one in the shop. Then again if they don't seem to want to, or claim that they can't, then probably not the best place to take it.
Rather than concentrating on looking for dealers willing to work on the Clarity, better to just try and determine the overall satisfaction of the dealership service department from online reviews. A shop that does reliable work in general should have no problem working on a Clarity.
As for sold only in California, that was true for most of 2019, but since then Honda has been selling limited numbers in other states as well.