Add the following to /opt/nginx-proxy/vhost.d/default

location ~ /auth-(.*) {
        internal;
        proxy_pass http://organizr/api/?v1/auth&group=$1;
        proxy_pass_request_body off;
	proxy_set_header Content-Length "";
}

For each service you want Organizr Auth on create a file called service.domain.tld_location such as sonarr.domain.tld_location with the following content

auth_request /auth-2;   # use whatever auth number you want depending on desired access level
proxy_set_header Accept-Encoding "";

If you want a failsafe BASIC auth for things like nzb360 create a htpasswd file at /opt/nginx-proxy/htpasswd/failsafe and add something similiar to below

satisfy any;
auth_basic "Failsafe Authentication";
auth_basic_user_file /etc/nginx/htpasswd/failsafe;

repeat the above process by creating a file for each service

If you have multiple services with the exact same permission level sonarr, radarr etc you can symlink the files however I use subfilters to inject custom CSS in mine so I have a separate file for each.

Organizr Authentication Levels

0=Admin
1=Co-Admin
2=Super User
3=Power User
4=User