You could use a tool like easypki that allow you to manage a testing CA, whose root cert you can import into your browser. Maybe use a different browser profile

You could use a tool like easypki that allow you to manage a testing CA, whose root cert you can import into your browser. Maybe use a different browser profile so a compromise of the CA keys would not allow anyone to compromise your banking sessions, too. https://github.com/google/easypki https://github.com/google/easypki But sure, if you're using Let's Encyrpt in production, this won't approximate your production setup in testing.