Apple is working on Password Manager Resources. A resource to share password rules, the URL for a password change, and combines URLs that support the same login. It is ready to be implemented into password managers today.

From their own GitHub:

Having password managers collaborate on these resources has three high-level benefits:
By sharing resources, all password managers can improve their quality with less work than it'd take for any individual password manager to achieve the same effect.
By publicly documenting website-specific behaviors, password managers can offer an incentive for websites to use standards or emerging standards to improve their compatibility with password managers; it's no fun to be called out on a list!
By improving the quality of password managers, we improve user trust in them as a concept, which benefits everyone.

This is something Proton Pass should definitely support.

https://github.com/apple/password-manager-resources