ELI5: How secure would duckdns + nginx be for remote access?

[TheDreadPirate]

You have to keep in mind that we are all small fries. No hacker with any skill is going after us.

Keep your system up-to-date
Use a reverse proxy
Use legit certs for https
Hide usernames from the Jellyfin login screen
Use non-standard https port to minimize randos finding your jellyfin
Setup fail2ban to ban the rare rando that finds your server

Running on a non-standard https port is big, IMO. I've yet to see any failed login attempts on my Jellyfin from rando IPs.