I’ve downloaded bunch of Jellyfin apps from flathub and AUR. There’s nothing like in the Windows where you will be directed in a browser and let’s you host from it.
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Did you start/enable the jellyfin.service systemd unit, as mentioned in the Arch Wiki?
https://wiki.archlinux.org/title/Jellyfin
In the same Wiki page it is mentioned that in order to configure Jellyfin, you have to browse to http://localhost:8096/ (after enabling the systemd unit).