If you are signing up for a new bank account with Mercury, they will a series of questions in their sign-up flow to verify your company's details. They ask for company information to prevent fraud and to fulfill their Know-Your-Business (KYB) requirements, especially in response to the Silicon Valley Bank collapse last year.
Asking for your address is one part of their KYB requirements, along with other measures they take to evaluate risk.
In their sign up flow, they will ask what your company's legal address is.
Add your Stable address there.
Next, they will ask where you do most of your work. If your company is remote, you should use your residential address. International addresses are also accepted.
Since you are not physically working at the Stable address, you should not use your Stable address here.
This will only be used for Mercury to verify your company's details to open your account, and to help fulfill their Know-Your-Business requirements. They will not publicize or otherwise use this information.
Once you're completed the sign-up flow, Mercury will evaluate the details your provide, and you'll be able to use your Stable address as your main company address going forward.