Don't worry about the UDP ports, they're only needed on the LAN and only in certain conditions. Basically Jellyfin uses them to "announce" things to the LAN.

On 7359 it announces clients where to connect; this can help you when first starting a client to let it connect automatically instead of you having to enter http://IP or https://jellyfin.mydomain.com.

On 1900 it advertises itself as a DLNA server. This is only relevant if you have other DLNA-capable devices. DLNA is a cool protocol that allows devices to act as server, controller or renderer and to cooperate to cast streams. For example you can use your phone as a DLNA controller to get media from Jellyfin acting as a DLNA server and cast it to a TV acting as a DLNA renderer. If your TV has DLNA capability then you may be interested in the BubbleUPnP phone app which can act as a controller, and that's when you may be interested in enabling 1900.

Or you can comment out the "ports:" section in your config and say "network_mode: host" instead and all 4 ports will be mapped automatically and work as intended (it's what I do).

So far so good. The URL is correct, because its the external address. You also don't need to publish both http and https ports. I only map external https to internal http but you can do https to https. No serious modern browser tries http first and because I always force https anyways, it doesn't need to be public. Only the reverse proxy may need it, for Let's Encrypt.

Both UDP aren't needed for public access. I only have mapped 8096 to my reverse proxy and it works.

I believe the UDP ports are for discovery on your local network so no need to handle them with your reverse proxy. If you've got them passed through docker your local devices should pick them up.

They're also not required since you can always just enter the address manually. I don't bother passing them into my container.