"Home wiki" is a concept that comes up from time to time within the movement (examples: T147696, Community Insights sampling, the Universal Code of Conduct Coordinating Committee Charter).

However, even though it's useful in many situations to systematically decide the home wikis of users based on their on-wiki contributions, there's no standard way of doing this. In two of the examples linked above, I used users' top wiki by edit count, but with each Wikidata edit counted as 1/10, because they are so granular that they accumulate much faster than on other wikis. But it's possible there's a much better way (e.g. top wiki by editing session length?). And, in any case, enshrining a standard requires seeking out and considering comments and then publicly proclaiming the choice.