Hey I actually got the joke

So what is it? 🧐

The sign is a subtle joke. The shop is called "Sneed's Feed & Seed", where feed and seed both end in the sound "-eed", thus rhyming with the name of the owner, Sneed. The sign says that the shop was "Formerly Chuck's", implying that the two words beginning with "F" and "S" would have ended with "-uck", rhyming with "Chuck". So, when Chuck owned the shop, it would have been called "Chuck's Fuck and Suck".

This is just stupid. Clearly the old store would have been called Chuck's feed and seed, it literally says so on the sign

That is subtle alright

Chuck's Feeduck and Seeduck

it says "formerly chuck's" so it was called "chuck's feed and seed". for reality where it was called "chucks fuck and suck" current name would be "sneeds feed and seed, formerly chucks fuck and suck"

You are wrong and you know it. Because if you were right, there weren't any joke there.