Directus under non root path with nginx

.env

DIRECTUS_KEY=<...>
DIRECTUS_SECRET=<...>
DIRECTUS_DB_DATABASE=<...>
DIRECTUS_DB_USER=<...>
DIRECTUS_DB_PASSWORD=<...>
DIRECTUS_CACHE_ENABLED=true
DIRECTUS_CACHE_STORE=redis
DIRECTUS_ADMIN_EMAIL=<...>
DIRECTUS_ADMIN_PASSWORD=<...>
DIRECTUS_PUBLIC_URL=https://<server_name>/directus/  # server_name is the one used in nginx. Note the slash at the end.

directus-nginx.conf

server {
   listen 0.0.0.0:443 ssl;
   server_name <server_name>;
   ssl on;
   ssl_certificate <ssl_certificate_absolute_path>;
   ssl_certificate_key <ssl_certificate_key_absolute_path>;
   ssl_prefer_server_ciphers On;
   ssl_protocols TLSv1 TLSv1.1 TLSv1.2;
   ssl_ciphers ECDH+AESGCM:DH+AESGCM:ECDH+AES256:DH+AES256:ECDH+AES128:DH+AES:ECDH+3DES:DH+3DES:RSA+AESGCM:RSA+AES:RSA+3DES:!aNULL:!MD5:!DSS;
   
   
   location /directus/ {  // note the slash here
       proxy_set_header   Host $host;
       proxy_set_header   X-Real-IP $remote_addr;
       proxy_set_header   X-Forwarded-For $proxy_add_x_forwarded_for;
       proxy_set_header   X-Forwarded-Host $server_name;
       proxy_set_header   X-Forwarded-Proto $scheme;
       proxy_buffering    off;
       proxy_pass http://127.0.0.1:8055/;  // note the slash here too
       proxy_redirect off;
   }
}

docker-compose.yml

version: '3'
services:
  directus_database:
    image: postgres:12
    volumes:
      - directus_db:/var/lib/postgresql/data
    networks:
      - directus
    environment:
      POSTGRES_USER: "${DIRECTUS_DB_USER}"
      POSTGRES_PASSWORD: "${DIRECTUS_DB_PASSWORD}"
      POSTGRES_DB: "${DIRECTUS_DB_DATABASE}"

  directus_cache:
    image: redis:6
    networks:
      - directus
 
  directus_server:
    image: directus/directus:9.0.0-rc.86
    ports:
      - 8055:8055
    volumes:
      - directus_uploads:/directus/uploads
    networks:
      - directus
    depends_on:
      - directus_cache
      - directus_database
    environment:
      KEY: "${DIRECTUS_KEY}"
      SECRET: "${DIRECTUS_SECRET}"
      DB_CLIENT: "pg"
      DB_HOST: "directus_database"
      DB_PORT: 5432
      DB_DATABASE: "${DIRECTUS_DB_DATABASE}"
      DB_USER: "${DIRECTUS_DB_USER}"
      DB_PASSWORD: "${DIRECTUS_DB_PASSWORD}"
      CACHE_ENABLED: "${DIRECTUS_CACHE_ENABLED}"
      CACHE_STORE: "${DIRECTUS_CACHE_STORE}"
      CACHE_REDIS: "redis://directus_cache:6379"
      ADMIN_EMAIL: "${DIRECTUS_ADMIN_EMAIL}"
      ADMIN_PASSWORD: "${DIRECTUS_ADMIN_PASSWORD}"
      PUBLIC_URL: "${DIRECTUS_PUBLIC_URL}"

networks:
  directus:

volumes:
  directus_db:
  directus_uploads: