The reason I ask is that I'm also curious if any of these zones encroach on their respective Roche limits.
As mentioned in the comments, your question kind of has two parts.
First are M stars. These are proper stars, having hydrogen fusion, and are actually quite terrible for any kind of life. The reason for this is the incredibly intense magnetic fields and fully convective nature of these stars. The dynamo effect (moving charged liquids creating magnetic fields) is largely to blame here, and is especially bad since from surface to core you have full convection (whereas in larger stars, you have confection regions of smaller fractions of the star). These magnetic fields lead to terrible, terrible stellar weather that would likely wipe out any living thing, especially given the fact that a planet would have to be so close to be in the Goldilocks zone.
Next are the L, T and Y ‘stars’. These objects are brown dwarfs, but brown dwarf specialists often still refer to them as stars, and rightfully so to an extent; brown dwarfs still have fusion happening in them, but not hydrogen fusion, mostly deuterium and sometimes lithium fusion. This isn’t enough to keep the brown dwarf at a stable temperature, however, and so brown dwarfs progressively cool down throughout their lifetime. They can get pretty cold in comparison to hydrogen fusing stars, and so the habitable zone will change over time, making the zones much less Goldilocks than we’d like for anything to realistically survive. Below is a visual that shows much better than I could say exactly how it evolves. Credit to Bolmont et al. for the data, and this website for the visualization :