I use a datapack on my server with plugin MythicMobs that adds custom mobs. I’m having an issue with one of my mobs - the health bar is glitchy, and I would like to remove the health bar entirely. Do you have any command in the function that can exclude specific mobs?

Yes. I believe the global.ignore is a common tag that you can add to an entity that datapacks use to ignore them, which this one employs. You can also use healthindications.ignore if you want it to be more specific.