I think I have found the issue. I used strace to see what messages knot
is sending to the systemd socket. When reloading, it sends RELOADING=1.
However, it is *not* sending the MONOTONIC_USEC= message. This makes
"systemctl reload" hang.
When using "Type=notify-reload", the MONOTONIC_USEC message is also
required as documented in the systemd.service man page.
Regards,
Anand