The pages https://www.passbolt.com/blog/openid-for-sso and https://www.passbolt.com/docs/hosting/configure/environment-reference/ both mention an environmental variable PASSBOLT_PLUGINS_SSO_PROVIDER_OAUTH2_ENABLED where the T and H in OAUTH2 are mixed up.
This creates problems when searching for the variable in the publicly accessible code. As a pro feature, it does not seem to be included there, neither in passbolt_api nor passbolt_docker.