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Firefox Has Quietly Integrated Brave's Adblock Engine
(itsfoss.com)
This is a most excellent place for technology news and articles.
I wouldn't think so. I would also assume that direct DNS requests to external servers aren't allowed in the firewall. But even if they are, they probably can't use a non-company DNS server if he needs to reach internally hosted services. So it would at least require using different browser for internal and external browsing, assuming DNS requests to external servers really are allowed.