openssh unix dev - Oct 2021 - More information/questions on my Firefox not working with 'ssh -D'

It seems that Firefox is rejecting the connection before it even gets
to the destination web server.

I am trying this now with my virtual server at isbd.uk.

I am setting up the ssh proxy from my desktop machine as follows:-

    ssh -fTnN -D 1080 chris at isbd.uk

I configure Firefox to use the proxy and when I try and connect I get
the security failure.

However there is no connection at all that reaches the apache2 web
server at isbd.uk, thus Firefox is rejecting the connection because of
something it doesn't like in the ssh tunnel.

Is it possible that it's somehow checking if there's a certificate for
my desktop machine that's running the ssh proxy command?  Is there any
way to debug what's going on between Firefox and the ssh tunnel?

Adding -vvv to the ssh proxy command tells me very little except that
there's lots of activity! :-)

-- 
Chris Green