I am not conversant with stuff handled by wireshark and may not be able to make sense out of the output.
However some additional relevant information is that being a single desktop user I use Net Manager and not Wicked. If I disconnect the internet via Net Manager the FF loads immediately and the connection can be remade at once. May be I have some setting incorrect in the Network Manager. What I can see are:
In the tab under Wired Autonegotiate is on.
802.1x Security is off
IPv4 tab Method Automatic is on, rest is blank and so are the routes.
IPv6 tab also method is automatic. This is where I have a doubt. My service provider does not cater for IPv6 as yet. Will setting this to Ignored turn off IPv6 hunting? I think I will try it.