@Brennan Phoenix I wholeheartedly agree with your excellent post. It is great that you have"pointed the finger" so well, with facts and figures that they cannot refute and excuse.
As you and others are saying, this current state of affairs with such an important Smart TV function (a workable and updateable browser), compared with the equivalent Android situation, positions LG in a very bad light compared with other manufacturers. This has certainly opened my eyes VERY WIDE, so when I am ready to change my TV, LG may well be very low down the shopping list!!
Since I originally posted this question, several things have happened. I have had several different versions of the Plex Server App on my QNAP NAS, and also there has been an update to the Plex Client App on the LG TV. Anyhow the upshot of all this is that my Plex on LG has been working well for about 6 month or so now, and to be quite honest, I'm not sure what has resolved the issue. I did not try your method, only because my thought was if it is working now then don't change anything... ;-)
What you said in your YT video made sense though.
@Akash Akash FYI: just because a web site shows something is a JPG or JPEG file, it is NOT necessarrily that file type. It might surprise you (or not), that the TEXT for any link in any page anywhere, can in reality be something entirely different. That in itself is one of BIGGEST security issues on the Internet today, and is down to how HTML is defined to work as it does. Many users do not even know that (on a PC browser anyway), placing the mouse-cursor over a link will show the REAL URL LINK for what the text represents. Likewise I could take any file (say a bad malware file, like a .EXE), and rename it as goodfile.jpeg and when you click on it to call your photo viewer, it might try to execute something bad, and put a trojan on your PC.
A TV browser may well be designed to check the REAL file type, and ignore it if it was not a real picture file.