This falls into the “how would they know about it?” category, but that doesn’t mean it’s not illegal or that you wouldn’t get prosecuted if they happened to find it. Sort of like growing your own personal stash of marijuana.
More than that, what are they actually trying to enforce? In the USA it’s excise tax. The TTB cannot possibly go after home distillers making quantities that you’d make with a stovetop still. It’s like $2.70 per gallon for small producers. Obviously in countries that have stricter alcohol laws, the math might be different.