Well, that's not certain. My point was really that the regs don't say anything about "official" charts. The question is how you interpret "suitable". Some countries have made clear that electronic charts are ok, other have said nothing.

You can't really make that comparison because you do need mechanical backup instruments if you have a glass cockpit.

I always carry some kind of paper chart as backup, but maybe not always ones that would be sufficient as primary charts.

Anecdotally, most authorities interpret the requirement like this: as the pilot in command, you must carry sufficient information to be confident that you can conduct the flight safely. That seems sensible to me.

I found the Guidance Material (GM) to NCO.GEN.135. It says:

The documents, manuals and information may be available in a form other than on printed paper. An electronic storage medium is acceptable if accessibility, usability and reliability can be assured.

So electronic charts are definitely ok as long as you are sure that your device doesn't stop working.

So, can anyone be sure, her/his device will never quit working?

You can never be sure that your engine doesn't stop working. Or that the paper map blows out the window.