Entware-3x

On new QNAP devices Entware-3x is used instead Optware or Entware-ng.

https://github.com/Entware-for-kernel-3x/Entware-ng-3x/wiki/Install-on-QNAP-NAS

In Download section you can find the install file.

On QNAP go to App Center and select manual install, browse install file and that's it, after the install, restart QNAP.

I connect with putty (ssh) and install what I need:

opkg install coreutils

opkg install findutils

opkg install bash

opkg install cron