Nonstandard subnational flag emoji: What part of the system is responsible?

So, I'm using Linux Mint 21.3 with MATE 1.26.0. I've noticed that my system supports a number of nonstandard flag emoji. I'm wondering what part of the system is responsible for this, if this is documented anywhere, and where the files or source for this can be found. Since I'm guessing not everyone is familiar: In addition to its mechanism for national flags, Unicode also has a mechanism for flags of subnational entities. However, this mechanism is mostly unused, with only the flags of England, Scotland, and Wales being officially supported according to the standard (the reason being, as I understand it, that the Unicode Consortium quickly realized that this would get completely out of hand if they allowed it to go any further). I've noticed that my computer actually supports a number of nonstandard subnational flags: American states and DC; Canadian provinces and territories; Mexican states and its federal district; and Northern Ireland (which officially doesn't even have a flag, but one is displayed regardless). Maybe there's more, but other subnational entities I thought to try (such as American territories or Australian states) didn't work. As an example, if your computer is like mine, this will display the flag of Delaware: 🏴󠁵󠁳󠁤󠁥󠁿 (my apologies to the Unicode Consortium for including a nonstandard emoji in general interchange! :P ) You might be wondering, why would I even think to try this, given that certainly I've never seen such nonstandard emoji in the wild, and had to assemble them myself out of the necessary non-printable code points (I mean with a script obviously, not by hand!), after inferring what those would be? The answer is that I got curious about the possibility after seeing [this MIT Mystery Hunt puzzle](https://puzzles.mit.edu/2024/mythstoryhunt.world/puzzles/crossed-fingers-memo-puzzle) the other year, which includes some US state flags as "emoji". Of course, the emoji in that puzzle are actually images, so there's no requirement for them to be actual emoji on anyone's system, but it got me wondering about the possibility, leading me to try out creating such nonstandard emoji on my own system, and, to my surprise, it worked. (I wonder if the writers of that puzzle were aware of this? Just realizing I didn't think to try contacting them... oh well.) (Edit: Actually, maybe I have seen this in the wild on one occasion? I forget, my memory's a bit fuzzy here. It's not important to the question anyway.) Anyway yeah this has been bugging me and I'm wondering if anyone knows what is responsible for this and where I could find more info. Thanks all!