Usually, I would click on the extension icon and then click a button to login. Does not work in this case (firefox)
Hey @OnlyCS and welcome to the community,
The page you’ve shown here is known as a basic authentication login or basic auth prompt.
Bitwarden can autofill and work for these, but there are some requirements such as being non-interactive and you must have only 1 marching login entry.
See more here for details