Heres what I’m running:

authentication_backend:
  file:
    path: '/config/users_database.yml'
    watch: false
    search:
      email: false
      case_insensitive: false
    password:
      algorithm: 'sha2crypt'

access_control:
  ## Default policy can either be 'bypass', 'one_factor', 'two_factor' or 'deny'. It is the policy applied to any
  ## resource if there is no policy to be applied to the user.
  default_policy: 'deny'

  networks:
    - name: 'internal'
      networks:
        # - '10.10.0.0/16'
        - '192.168.1.0/24'
    - name: 'VPN'
      networks: '10.0.1.0/24'

  rules:
    ## Rules applied to everyone
    - domain: '*.mydomain.com'
      policy: 'one_factor'

session:
  ## The secret to encrypt the session data. This is only used with Redis / Redis Sentinel.
  ## Secret can also be set using a secret: https://www.authelia.com/c/secrets
  secret: 'insecure_session_secret'

  ## Cookies configures the list of allowed cookie domains for sessions to be created on.
  ## Undefined values will default to the values below.
  cookies:
  #   -
      ## The name of the session cookie.
    - name: 'authelia_session'

      ## The domain to protect.
      ## Note: the Authelia portal must also be in that domain.
      domain: 'mydomain.com'

      ## Required. The fully qualified URI of the portal to redirect users to on proxies that support redirections.
      ## Rules:
      ##   - MUST use the secure scheme 'https://'
      ##   - The above 'domain' option MUST either:
      ##      - Match the host portion of this URI.
      ##      - Match the suffix of the host portion when prefixed with '.'.
      authelia_url: 'https://auth.mydomain.com/'
storage:
  postgres:
    ....

identity_providers:
  oidc:
    ## Cross-Origin Resource Sharing (CORS) settings.
    cors:
      ## List of endpoints in addition to the metadata endpoints to permit cross-origin requests on.
      endpoints:
         - 'authorization'
         - 'token'
         - 'revocation'
         - 'introspection'
        #  - 'pushed-authorization-request'
        #  - 'userinfo'

      ## List of allowed origins.
      ## Any origin with https is permitted unless this option is configured or the
      ## allowed_origins_from_client_redirect_uris option is enabled.
      allowed_origins:
        - 'https://mydomain.com/'
        - 'https://grafana.mydomain.com/'
        - 'https://wiki.mydomain.com/'
        - 'https://foodz.mydomain.com/'

      ## Automatically adds the origin portion of all redirect URI's on all clients to the list of allowed_origins,
      ## provided they have the scheme http or https and do not have the hostname of localhost.
      allowed_origins_from_client_redirect_uris: true
    ## Clients is a list of known clients and their configuration.
    clients:
      - client_id: 'grafana'
        client_name: 'Grafana'
        client_secret: 'XXXXXX'
        public: false
        consent_mode: 'pre-configured'
        authorization_policy: 'one_factor'
        require_pkce: true
        pkce_challenge_method: 'S256'
        redirect_uris:
          - 'https://grafana.mydomain.com/login/generic_oauth'
        scopes:
          - 'openid'
          - 'profile'
          - 'groups'
          - 'email'
        userinfo_signed_response_alg: 'none'
        token_endpoint_auth_method: 'client_secret_basic'
      - client_id: 'wiki'
        client_name: 'Wiki'
        client_secret: 'XXXX'
        consent_mode: 'pre-configured'
        public: false
        authorization_policy: 'one_factor'
        require_pkce: true
        pkce_challenge_method: 'S256'
        redirect_uris:
          - 'https://wiki.mydomain.com/oidc/callback'
        scopes:
          - 'openid'
          - 'profile'
          - 'groups'
          - 'email'
        userinfo_signed_response_alg: 'none'
        token_endpoint_auth_method: 'client_secret_basic'
      ....

Then my users_database.yml looks like:

users:
  authelia:
    disabled: false
    displayname: "Test User"
    password: ""
    email: authelia@authelia.com
    groups:
      - admins
      - dev
  user001:
    disabled: false
    displayname: 'User 001'
    password: "$6$rounds=50000$XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX"
    email: test@gmail.com
    groups:
      - admins
      - users