Ha ha, good one. I stand corrected, probably, if I didn't mention earlier, that the yogurt-making procedure I gave, was specific to the warmer temps of most regions of India. And even some of those regions get pretty cold in winter (at least by sub-tropical country standards).
>a nice place that's kept around 43degC in a house that's usually around 17degC overnight.
Like where I am now, min temp has been 7 C or even 6 C at night lately, and in some places I've been (which are not even in northern India, which is colder), the min has been known to drop to 2 C at times, though rarely. Goes to zero or below, in some places, sometimes, of course.
(I do know that places in the world further north (or south) can get a lot colder, like -40 C (= 40 F) or more.)
Welcome to Saskatchewan, Canada, where there aren't any places in the house that are at the right temperature in the winter :). That's roughly what the Instant Pot does though. You bring it to a boil first, let it cool off, and then it'll keep the pot at the right temperature while it ferments. Nothing special, other than a nice place that's kept around 43degC in a house that's usually around 17degC overnight.