Currently, Automated Clearing House (ACH) deposits/transfers from a linked bank account is the only method available to fund your Alpaca Account.
Bank Transfers & Linking
A collection of 8 articles
Q - How do I initiate a deposit from my linked bank account into my Alpaca Account?
How do I initiate a withdrawal/transfer from my Alpaca Account to my linked bank account?
Q - How do I link my bank account to my Alpaca account through electronic authentication?
You may try this alternative bank link method using micro-deposits, which links with your bank account and routing numbers.