Opening the link you shared on Android here from discourse, it takes a good while to load in chrome.
If I had to guess, it simply takes a good long while, but that is a bad user experience to begin with.
If you control the target website, I suggest you add some in-site logging into the DOM to debug it, that’s how I have debugged my own extension on mobile, but you can also use adb to read the logcat live if set up correctly and that may catch some additional info if you are lucky. (Note that I have not tested it and don’t know how useful logcat is for it, but it may be worth a shot if you have no other option.)
Other than that: Your target app seems to, in the end, just open a VOD/live stream of LEC/RiotGames - you should most likely just link to that directly, so the user stays within the Twitch App, which is a WAY better experience on mobile than having the embeds visible in a WebView.