I have set the mfe-lms-production-settings patch MFE_CONFIG['SHOW_REGISTRATION_LINKS'] = False and on the regular login page (/authn/login) it does hide the Sign Up link however on the new page at {LMS_HOST}/catalog/ the Sign Up button remains visible.
The openedx-lms-common-settings patch FEATURES['ALLOW_PUBLIC_ACCOUNT_CREATION'] = False does still prevent a user from registering, however the links to register remain visible