@dicknskip: There's another person at launchpad doing sigil PPAs. His routine is to compile from the latest git every couple of weeks or so and make PPAs available for the releases of Ubuntu still supported by Canonical. Frankly, it's a little too bleeding edge for me, but other, braver, souls might like to know about it. Start at
https://launchpad.net/~sunab/+archive/sigil-git
Since this is very volatile code, should you have problems, you are on your own. But do let us know how it goes if you try it.