It’s possible at the client level, here are the steps:
Create two payment gateways for the same gateway with different payment methods enabled
Edit the client’s settings to remove the gateway containing the payment method they shouldn’t use
Edit the company settings to remove the gateway containing the payment method other clients shouldn’t use
Note: since you’ll have the same gateway twice I suggest using the label field on the gateway settings tab to give each record a different name. You may want to consider configuring this at the group level if it will apply to more than one client.
So, I am able to add a 2nd instance for Stripe Connect, but I am unable to complete the setup for the 2nd instance, when attempting to do it I face the following message:
When I set a client to pay using the new instance, there is an error for gateway not configured. There are red warning triangles next to the new instance as I can not complete the configuration.
You can try manually specifying the Stripe API key for the second Stripe gateway, instead of using the OAuth connect login.
Settings>Payment Settings>Setup Stripe> close / go back and edit it, set your API keys under Credentials. Name this gateway something else (Settings>Label).