Selfhosted

Never call yourself an idiot. Not a good IT engineer? (Just saying, I don't know you) That doesn't make you stupid at all.

For whatever it is worth to you I've hardened my jellyfin docker compose this way. I'm obscuring some things in this that are local to my network.

The container is read only. It mounts the media read only. It should be fairly isolated from getting privileges it shouldn't have. The only things lost in this setup are the ability to delete media from a jellyfin client (something I never do) and the ability to manipulate files directly stored with the media. I use bazarr for subtitles so don't need jellyfin to download them and I don't keep trickplay or any other jellyfin metadata related files alongside the media. I feel pretty confident with this that even if the jellyfin codebase had a serious 0 day that the worst I'd lose is metadata and server setup, and important config files I have backing up to another machine.

I'm sure there's things I've overlooked with this setup so I'm very open to being told there's a better way to do something.

services:
  jellyfin:
    image: jellyfin/jellyfin:latest
    container_name: jellyfin
    restart: unless-stopped
    mac_address: OBSCURED # see macvlan note below
    hostname: jellyfin
    user: ${PUID}:${PGID}
    group_add:
      - "992" # my render group id
    security_opt:
      - no-new-privileges:true
    cap_drop:
      - ALL
    read_only: true
    tmpfs:
      - /tmp:exec,nosuid,nodev # exec some plugins can write to /tmp, no-nosuid,nodev for security
    networks:
      macvlan:
        ipv4_address: OBSCURED
    healthcheck:
      test: [ "CMD", "curl", "-fsS", "http://127.0.0.1:8096/health" ]
      interval: 1m
      timeout: 10s
      retries: 3
      start_period: 30s
    environment:
      - TZ=${TZ}
      - JELLYFIN_PublishedServerUrl=OBSCURED
      - JELLYFIN_DATA_DIR=/config/data # consolidates these dirs under /config, migrated from linuxserver.io setup
      - JELLYFIN_CONFIG_DIR=/config
      - JELLYFIN_LOG_DIR=/config/log
      - JELLYFIN_CACHE_DIR=/config/cache
      - HOME=/config
    volumes:
      - ./jellyfin:/config
      - ${MEDIA}:/media:ro
    devices:
      - /dev/dri/renderD128:/dev/dri/renderD128 # isolate to just the renderD128 device
    device_cgroup_rules:
      - 'c 226:128 rw' # further limits access for the renderD128 device

networks: # I went with macvlan to preserve mdns for local discovery, otherwise you need to use host level networking
  macvlan:
    driver: macvlan
    driver_opts:
      parent: OBSCURED # Replace with host network interface name (find via: ip route | grep default)
    ipam:
      config:
        - subnet: OBSCURED/24 # Your local LAN network CIDR
          gateway: OBSCURED # Your local router IP address

Not sure why nobody here recommended netbird reverse proxies. It has crowdsec out of the box plus blocking/allowing ip ranges. On top of it, it also support pin or password based auth, so you can have 2 layers of auth.

But i haven't hosted jellyfin yet, only opencloud and a couple others. Haven't seen anybody pwning it based on the logs

Backup.
Update.
Don't keep all in one place.
Update.
Don't forget to backup.

So the public services are purely for private use, to sync your mobile devices? You can install Wireguard on Android, send them over there. Though for e-reader, since they are Kobos (basically Android), you can trick it to install the app. Or even another launcher/book reader.

crowdsec is super easy to setup

I use Pangolin on a kinda cheap VPS on Hetzner (they're now a bit too pricey), and route my services through Site Connectors (Newt, it's called). Dealing with opening my firewall is a pain I don't wanna think about, but Pangolin creates a websocket and can do NAT traversal from the Site Connector, so no swiss-cheesing your firewall.

It's nice because you can contain different services with VLANs to further segment and protect your network, and each Site Connector can work for many services (if there's no firewall rules restricting it/VLANs) or you can put a Site Connector on each server individually, if segmentation is important to you.

Get Jellyfin off the open internet. For family who'll never install a VPN app, the setup that holds up is WireGuard on their router, or Tailscale on whatever TV box they use, set up before it ever ships to them. They never see it. If something has to stay public, CrowdSec plus Pocket-ID is a lot lighter than Authentik for three users. I'm building a home box that ships locked down like this by default, so I'm curious: which broke first for your family, remote access or the logins?

If you don't mind I'd share my scenario with you, but I'm far from a professional myself, so in the same time I'm also asking any thought about my own approach.

For my public facing services (e.g. Nextcloud) I've created a separate VLAN which is completely isolated from the rest of the system, I've deployed an nginx LXC with Crowdsec/fail2ban, and opened very specific "pinhole" style firewall rules towards the service layer VLAN in OPNsense. I've also separated this service / app VLAN layer from the database layer (which is another VLAN with strict firewall rules and SSL). For authentication I use what the service offers natively, except for some cases of keycloak / hardware key.

Based on my research, this should be a solid baseline, but honestly noone more knowledgeable than myself has confirmed it, so take it with a grain of salt.

There is some great advice in here but I wanted to throw my two cents in by saying bollocks to Hetzner, they get circlejerked far too much. Go with Contabo instead, 4 core 8GB VPS with 100GB SSD is $5 a month right now and has a generous 30TB/month bandwidth allowance.