Somehow systemd does not run in the debian-chroot, so in case inetd is working for you, here’s how:
ssh to your synology
sudo -s chroot /volume1/@appstore/debian-chroot/var/chroottarget /bin/bash apt install wget tcpd zip unzip openssl lftp openbsd-inetd
Install software of choice. Then:
service openbsd-inetd start exit
Auto-start the inetd service with the debian-chroot:
sqlite3 /volume1/@appstore/debian-chroot/var/debian-chroot.db
INSERT INTO services VALUES ('0', 'INETD', '/etc/init.d/openbsd-inetd','ps -p $(cat /var/run/inetd.pid)');
.quit