One of the issues with playing video directly in the VaM internal browser is that VaM has no security involved, hence it only run stuff that is either integrated from the HUB website or really basic HTML 5.X, CSS and Javascript stuff.
Most of the video hosting website like Youtube, YouPorn, RedTube, etc. uses a bunch of overlaying Javascript with custom reference to some remote library to play a video. From the code that detect, load and play ads to the simple initial loading sequence (the big "Play" button that appears in the middle of the video player if not played automatically) and even to the sequencing and data-fetching codes that might run with the video. (You know, the code that detect how many views are active on a video, who's watching which part and so on.)
To protect their website, most of the video hosting website uses referential methods to load javascript. (Basically 1 javascript code load and cache a bunch of remote javascript codes that allows the player to access the website video content and cache it.) This why, in recent years, lots of the video downloader pluging/extension just stopped working unless they were precisely made for a website's loading method.
The VaM browser doesn't load remote javascript codes, but only whatever is on the first layer unless it's part of the HUB which, from what I have seen, VaM has a bit of an integration of the stuff related to it. (Basically, it can interpret the
page as every pages like that follows the same strict rules.) This is also why said Browser has a big warning telling you to not load any web page which had stuff you don't know about or you do it at your own risks.
Imagine that Steam's browser had this issues since its creation and Valve ended up telling everyone "
We only made the browser to allow people to visit a shared platform around Steam for all devices and its community and not to visit anything else so we just don't care if X website or feature doesn't work anymore."
To answer the question about how to publish video/trailer on the HUB, the answer is actually simple:
Don't do it on the HUB.
Instead, put a direct link to whatever trailer on remote site that tell something like "Click here to check the trailer on XXXXX" and, under this link, put 4 or 5 images taken from the trailer (the best that demonstrate the content). Anything more picture is just a waste of both your and the user time because it's a pain to scroll down in the in-game Browser and it slow down the loading time when accessing your content's page.
