Opera natively supports MHTML, but you have to manually enable it.
Into the address bar and opera will work with MHT files. It sucks that everyone told you there is no solution to this. There is. I've been using it since Opera 20.
As to understand what I mean, give a try to memorize the thumbnail
of this link on the Speed Dial icon
this is the image I want for that Speed Dial Icon
(usually you select the image clicking on the red heart that appears on the bar at the Top right of the window)
p.s.: as told, sometime to memorize the image is easy other time there is no way (Why ??)
Do a backup of Opera's profile folder.
Thanks, Many Thanks
..... but it was your choice to use a testing version of a software .....
My fault, I didn't know I was using a testing version
Till sometime ago I decided when and if I want to upgrade the Opera version on my PC
but now seems this isn't under control of the user and the upgrade are automatic