FWIW: this is from a couple weeks ago -
Curious - Calibre Install asks for a restart
I've installed a later version of calibre since then, did not get a restart needed popop, so it was a 'one off'. Very occasionally I have had installs of other programs do the same thing - I call them blue moon events.
Aside: I'm still using Sigil 0.9.13. Given 0.9.15 will be released soon, is there any reason I should not skip 0.9.14, there's nothing in it I need.
BR