Halo: The Master Chief Collection is available on Xbox Series X/S, Xbox One, and PC.
Postums) said that currently, there are no plans to add mod support to The Master Chief Collection on consoles, and that for now, 343 is focused on improving the modding experience on PC.
Meanwhile, Halo Infinite is launching for the same platforms later this year, though a specific launch date hasn’t yet been announced.
One of the ways they have done that is, of course, through mod support in the game.