Bypass SSO on Web

We have SSO active by default on our vault, which works great. But we now have some external users who need to access the vault, preferable on web, but they immediately get prompted to log in with SSO, but they do not belong to our organization. They can log in with their M-Files credentials on the classic web, but that version is so out of date that we don't want them to use it. How can we bypass SSO only for these externa users, without having to trouble our internal organization users to have to select if they want to log in with SSO or M-Files Login.

Thanks