Browsers were essentially purpose-built to render untrusted content.
Additionally, the build being distributed is Chrome 89.0.4389.114, and there hasn’t been progress to get it to build correctly on 90 or 91 for that matter. See the issue tracker with people saying the same.
There are 222 open issues as of now. Yes, seen through some.
I believe other browsers also have similar unresolved problems if you go through their forums. Don't expect all problems can be resolved for each browser.
Some issues from the forum
One (the Pandora.com issue) got feedback/suggestions but no reply from thread starter, so not sure issue resolved or still outstanding.
Two started a problem (block local IP address and Chromium 91 vaapi intel)
and said to give a try on the suggestions offered. After that silent........no reply on success or failure.
As for the Widevine user if he wants it he should not have use UC (Eloston) because Widevine belongs to Google. Although the provision is there to install Widevine explicitly, it's not working. The provision of extensions installation allows one not to connect to Google Play Store directly for downloading and updating. However, Eloston will not guarantee the extensions will work and work correctly/safely.
getting HD video (Prime / Netflix .. etc) issue - Reply is "On Windows it requires VMP, see #1258 (comment). Basically we need a certificate from Google to include in the browser, which is very hard if not impossible." UC is supposed to be a de-Google browser.