I first upgraded linksys ea3500 with old openwrt firmware. I was unable to access gui. So I ssh into the router and applied these two commands:
opkg install luci
Then I was able to access the gui and upgraded to 18.06.0.
I forgot to appy opkg install luci-ssl command initially to enable ssl. How should I do this? Do I need ssl certificate? Can I use self signed certificate, if yes how to create one?