Run the following commands in terminal
# install prerequisites
sudo apt install apt-transport-https -y
# add gpg key
wget -O - https://repo.jellyfin.org/jellyfin_team.gpg.key | sudo apt-key add -
# add apt repository
echo "deb [arch=$( dpkg --print-architecture )] https://repo.jellyfin.org/$( awk -F'=' '/^ID=/{ print $NF }' /etc/os-release ) $( awk -F'=' '/^VERSION_CODENAME=/{ print $NF }' /etc/os-release ) main" | sudo tee /etc/apt/sources.list.d/jellyfin.list
# update software repositories
sudo apt update
# install jellyfin
sudo apt install jellyfin -y