Use Saml2Aws CLI as an alternative to SAML to AWS STS Key Conversion.
Install on Mac.
brew install saml2aws
saml2aws --version
Configure. Provide information.
saml2aws configure
It will create a ~/.saml2aws config file. Set session to 8 hours.
aws_session_duration = 28800
Login.
saml2aws login
After authentication and/or MFA, your ~/.aws/credentials will be updated.