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Manifest V2 phase-out begins
(blog.chromium.org)
This is a most excellent place for technology news and articles.
Like Chrome Firefox has an internal Task manager at: about:processes
You could try opening it in a second window. It might show you what causes the hang. There is also: about:memory to see where the RAM went. It's a bit more technical though.
Oh cool, didn't know that one yet, thanks a bunch!