Why, when I was a kid we had to go mine the coal ourselves, using our
fingernails to dig!

Obviously a clean burning fuel for indoors is a must but that aside I think
I would have enjoyed burning little crumbs of real coal especially for the
smell. Probably a pain to get a coal fire started though. I'm surprised
they didn't / don't just fuel these things with alcohol.

The reason an electrically heated boiler seems pointless is that with the
possible exception of an unverified reference to Italy having built
electrically heated steam locomotives anyone having electricity who desires
mechanical energy is going to use an electric motor!