It's possible you have a dependencies lock in place. Can you run
apt -y update without an error?
I just ran this several times on a couple of different machines and the users installed without issue.
!important! When creating a user, only use lowercase for the username
Password: (hit enter to generate a password) qbuser1
writing qbuser1 to vsftpd.chroot_list...[OK]
writing qbuser1 .rtorrent.rc using port-range (56815-58315)...[OK]
setting permissions ... [OK]
writing qbuser1 rutorrent config.php ... [OK]
Setting up autodl-irssi for qbuser1 ... [OK]
Setting up Deluge for qbuser1 ... [OK]
Created symlink from [email protected]ice to /etc/systemd/system/rtorrent@.service.
Created symlink from [email protected] to /etc/systemd/system/irssi@.service.
Created symlink from [email protected]ce to /etc/systemd/system/deluged@.service.
Created symlink from [email protected]rvice to /etc/systemd/system/deluge-web@.service.
Setting up modern file-system indexer (h5ai) for qbuser1 ...