Consider sentences of the form (correct me if I've got them wrong):
Mir ist langweilig / Es ist mir langweilig.
Dem Mann ist kalt / Es ist dem Mann kalt.
It's important not to use the nominative form (ich) for these pronouns as that would change the meaning of the sentences completely.
But what if the nouns in question are proper nouns / nouns without articles (which don't have any case markers)? How would it look then?
I did find the adjective gelangweilt that presumably could be used with a nominative noun, but I don't want to "cop out" and rephrase.
How would I indicate the dative case of a proper noun in this case without rephrasing (e.g. zu / nach John ist es langweilig)? Also, how does German solve such problems in the general case?