In English, if you have people you are friends with from a forum (online or otherwise), you could call them "forum friends". How would you say this in Latin? Can you decline forum as a genitive like amicī forī, or would that be more like saying they are friends of the forum itself? Would you use ablative case instead with a preposition?
Edit: I did some search and found this post regarding using a noun as an adjective, which got me thinking that there might be an adjective that means "associated with the forum" or similar.
There is the word circumforaneus, which has the following meanings:
itinerant, that travels to market; of/connected with business of/around forum
With this adjective, I could do something like:
Would this make sense?