Would Second Hand Expansion Packs Work?

The title is basically my question. The main issue I've researched is that an activation code would only work once, but that's for registering the pack with your account. On a previous thread from 2012, one of the commenters said that you don't need to register online for it to work and that the only reason to register would be for registration rewards. However, it's 2021 now and I don't know if that answer still applies.

So if I found an expansion pack pc dvd rom at a thrift store, would I be able to use it with my game at all?