I have a QNAP shared drive that is visible and mountable in the Finders app but does not show up as a Time Machine backup disk

I am trying to setup time machine with a QNAP shared drive.

The drive is visible and mounted in the finders app; however it does not show up as a Time Machine backup disk. In fact I have no options listed in the "select backup disk ..." popup other than "other airport time capsule".

Is there a way I can force the time machine "select backup disk ..." to consider other options (like my QNAP remote disk that is visible in the finder)?

I'm using High Sierra on my MacBook Pro