I'm not sure I can even quite call it that. One signature part of that is that it has separate race and class like every other version of D&D except B/X, BECMI, RC.
It's a really well-curated mix of elements from OD&D, BX, 3E, 4E and 5E plus OSR /non-D&D elements like roll to cast, the talent progression tables, luck tokens, torch timers... Probably the single edition it takes the most important/central elements from is 3E (unified D20 mechanic, ability score progressions), but even that's pretty minimal.