Can a semicolon be a conjunction?

A semicolon isn't the only thing that can link two independent clauses. Conjunctions (that's your ands, buts, and ors) can do that too. But you shouldn't use a semicolon and a conjunction. That means when you use a semicolon, you use it instead of the ands, buts, and ors; you don't need both.

What can replace coordinating conjunctions in sentences?

When connecting two independent clauses with a comma and a word like “however” or “therefore,” you can either divide the sentence into two sentences, or use a semicolon, which can be used to connect two independent clauses without a coordinating conjunction.