IC wise, my bugout choice would be small olde skool diesel... but I won't drift off there, except to say.......
The tough thing for electric high-density power is storability, and portability.... meaning off-board, but close-by.
Land Rover Defender Jerry Cans Accessories and Auxiliary Fuel Tanks | LR Parts
Exterior fuel-cans are for more than looking butch, driving to Starbuks.... though they get used for that too.....
I can easily carry enough extra fuel to traverse my Province, and it's not a small one.
Not just keyboard talking..... I take at least 40L of extra fuel with me, remote drives in Canada, during Summer, non-emergencies.
I do get that this practice is not "normal", but is one option that matters to me....
I (honestly) look fwd to the the day that EVs are that easy to backup....
Rgds, D.