It totally depends on how you expose it to the outside world. If it’s exposed just like it is, it works fine with every device. If you put an authentication before it (e.g. Authelia), it can only be accessed by browsers from outside the network. That being said, it’s not recommended to expose Jellyfin directly, because there are a ton of security flaws. Best practice is to use a VPN
It totally depends on how you expose it to the outside world. If it’s exposed just like it is, it works fine with every device. If you put an authentication before it (e.g. Authelia), it can only be accessed by browsers from outside the network. That being said, it’s not recommended to expose Jellyfin directly, because there are a ton of security flaws. Best practice is to use a VPN