It’s best to get it directly from Plex and then Plex itself will notify you of new updates and you can download it right from that notice and update it manually in like 5 seconds. Been doing it that way for years and years on QNAP and Synology.
Linky: https://www.plex.tv/media-server-downloads/?cat=nas&plat=qnap
The QNAP store app is usually not that far behind either so might be something up there.
I agree with you about the “unusable” complaints - there are oddities I don’t like but getting around it isn’t much different so I totally second this about it being more of a knowledge\information problem in many cases.
Even in the beta we asked them to document some of the common things coming up that were just knowledge problems (how to disable discovery stuff at account instead of client, how to pin libraries using “favorite” and that it was account level now, using the back button instead of the d-pad on the remote, that the “snapback” feature for library navigation was added and how it works).
Plex has always had a habit of posting info somewhere - anywhere - and assuming every user should now be aware of it (I think sometimes that includes their internal spaces too). So many issues folks experience with Plex could be resolved with just accessible information. That doesn’t mean add an AI tool, just improve the documentation setup. For example, the current “documents” area doesn’t work very well unless you already know what to search for so simply making it more structured and browsable would be a huge improvement to help people find things they need to know but didn’t know they needed to know it. It’s a huge peeve for me. 
