Dozens !

Yep, that’s why I call that a tradeoff. Far from perfect and yet so much better than nothing.

Pros:

• Likely cuts 99.99% of attacks.
• Nothing to do on client’s end.

Cons:

• Whitelisting must be updated everytime the client address changes.
• Not 100% bulletproof as operators (notably for mobile networks) can NAT multiple connections behind a single publicly addressable IPv4 address.
• Also IP addresses can be spoofed but I doubt that would be a major concern here.

No, not for remote access over the internet.

For a remote and non-technical user I would say IP whitelisting offers a decent tradeoff.

On your end you expose your jellyfin port to internet, but restrict at the router level to your user’s client IP address as soon as you have it. Obviously in practice this works best if the address does not change often.