Very educative post, @jephline. What I use to back up my keys is protonmail. It's a highly encrypted email based in Swizerland. If you lose your pass to your protonmail account, you've practically lost all your information therein, since it cannot be recovered. Moreover, I think a combination of protonmail and an external hard drive to store my keys would be a near perfect solution, especially in these days of DDos attack. Cheers.

@maryfavour.