So, Nexus 3.22 OSS (latest OSS version) do not support SAML or OIDC, but the Pro version does [1], [2].
On the other hand, Nexus OSS supports LDAP [3].
Also, there is a Keycloak plugin for it [4], [5], which apparently supports:
Supports to map the Realm-Roles, Client-Roles and Realm-Groups of Keycloak.
Supports to map multiple Keycloak realms.
Supports Keycloak Single Sign On (SSO): sign-in and sign-out are all supported.
So, Nexus 3.22 OSS (latest OSS version) do not support SAML or OIDC, but the Pro version does [1], [2]. On the other hand, Nexus OSS supports LDAP [3].
Also, there is a Keycloak plugin for it [4], [5], which apparently supports:
[1] Nexus OSS vs Pro features. [2] https://help.sonatype.com/repomanager3/repository-manager-pro-features [3] https://help.sonatype.com/repomanager3/system-configuration/user-authentication/ldap [4] https://github.com/flytreeleft/nexus3-keycloak-plugin [5] https://devopstales.github.io/sso/nexus-sso/