Does the plaid link product (https://plaid.com/docs/link/) include non depository accounts? From what I've seen, it only seems to include depository accounts
Yes, it does.
For a full matrix of supported products by account type, see the API Reference.
Note that Link isn't in that table because it's the frontend used for every Plaid product, so anything that is supported by any Plaid product is necessarily supported by Link.