According to some of my tests, mods related to horse armor, for example: Diamethysts!, Epic Knights and addons, maybe some other mods that I haven't tested are all broken or have no animation, of course the armor bar still exists, the armor effect is the same. As for Cyclic mod, most of the items that increase horse abilities are not available for new mobs that replace vanilla horses, I think because new mobs are not considered "Horse" available to use Items. And I value efficiency more, so I would be grateful if someone could help me improve this compatibility in the next update.

Unfortunately I don't really use those mods so I won't be putting direct compatibility for those in at the moment, since I'm using my energy and time for other stuff. If they want to build compatibility with LO, though, through their own mod, they're very welcome to.

I'd suggest contacting them for stuff like that. It would also probably be much easier for them to do it on their end then it would for me to do it on mine, if I had to guess. Especially for the effects ones.

Otherwise, you can turn O-Horses off in the common config so you just get normal vanilla ones (which would be compatible).