Hello!  So, as you  already know, the Enchantment Glint for Horse Armor that was added for literally one snapshot has stopped working, but that's not the point.  The point of this bug report is that Netherite Horse Armor doesn't exist and Horse Armor Trimming in impossible.

I know, I know, I should just put this in the Feedback site, but sadly the Feedback site still won't let me log in.  So, as a result of that and the fact that nobody seems to read my Youtube Comments on the subject, I'm simply putting it on the record here that, despite Netherite and Horse Armor both existing, and despite the fact Armor Trims Exist and Horse Armor is a type of Armor, neither Netherite Horse Armor exists nor does the ability to trim Horse Armor with an Armor Trim.

I know there's a mod that could do that, but I'm not sure it's up to date, plus I don't use mods.  However, I do know that both Horses themselves as well as Pistons started out life as mods, so perhaps you could just utilize the mod that has Netherite Horse Armor and Horse Armor Trimming as a basis for adding in Netherite Horse Armor and Horse Armor Trimming.  You did that before after all with Pistons and Horses themselves, so I don't see why that would be an issue.

So, thus, those are my current issues with Horse Armor, it has no Netherite Variant, (which really irks me as my poor Horse and I can't have proper matching armor), it's enchantment glint is still missing, (even though it was there for literally one snapshot), and I can't trim my Horse's Armor to compliment mine.

And I can't send to the Feedback site because I STILL. CAN'T. LOG. IN!!!

Anyways, Rockatoa, Brickticks out!