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 IP or 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).