QNAP TS-421 plex server version 1.3 or higher required

I have a QNAP TS-421 NAS which I use via a Google Chromecast using iphone x with the plex app. The Plex iphone app when trying to connect to the NAS I am getting the message “plex server version 1.3 or higher required” I have attempted to update plex manually on the NAS but the update fails during installation. Please advise how I fix this?

I sadly had problems digesting what CPU is in your NAS, but sadly due to age (2013) suspect it’s Arm V5 based

If so, you are sadly out of luck here

https://support.plex.tv/articles/218212517-which-nas-devices-are-no-longer-supported-starting-with-0-9-17-0-server/

All I can suggest, is to use your QNAP as a file store for your medias, and run your PMS on another box