Excuse me for interrupting this conversation, but, what is the point
of making sure a browser is secure knowing there is a complete HIDDEN
OS running all the time? I have no idea what it does and what
functions it offers to the outside world. To learn about such
functions I must either believe Intel or accept what reverse engineers
found. The fact that even GNU/Linux cannot get rid of such an OS is
depleting me of motivation to seek a more secure system. For me, it is
becoming enough if I can use a computer and be cautious if I do not
want to disclose sensitive/private information.

I remember, more than a decade ago, when I still did not have an
internet connection, I was a staunch believer that security
necessarily implied NO NETWOK CONNECTION.

Sorry for my intrusive rant.

--
If you can't explain it simply, you don't understand it well enough.
(Albert Einstein)
If you cannot make abstructions about details you do not understand
the concepts underlying them.