Organizr auth working on Cloudbox

app.domain.tld_location

# FILE - /opt/nginx-proxy/vhost.d/app.domain.tld_location e.g sonarr.cloubox.com_location

auth_request /auth-2;
# optional failsafe basic auth
satisfy any;
auth_basic "Failsafe Authentication";
auth_basic_user_file    /path/to/htpasswd;


## Full group list
# 0=Admin
# 1=Co-Admin
# 2=Super User
# 3=Power User
# 4=User

## you may also be able to save this as default_location and it will work for all vhosts which don't have a individual configuration

default

# FILE - /opt/nginx-proxy/vhost.d/default

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

## Make sure to replace domain.tld with either organizr.domain.tld or if you have direct_domain enabled then just domain.tld

I also figured out you can use the container network alias for the Auth request:

## Organizr authentication

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

## End of Organizr Authentication

You can't use the container alias for the Organizr error pages though