I noticed that the ghostrays in the end only spawned in the vanilla end biome and doesn't spawn in modded end biomes and I did try to control the ghostray spawns with a spawn controller mod but they don't play nicely with the spawn controller mod by not obeying the spawn rules and completely stop spawning when I set the light limit rule for them, So it would be nice to make the ghostrays spawn in vanilla end biome and modded end biomes.

Ghost Rays spawn in all biomes with "END" tag except the central island. If they don't, that's probably because the owner of the modded end biomes clear out all entity spawns and just add their own mobs only.

I recommend using BiomeTweaker for this case, it works really well on adding mob spawns without much issues. Specified Spawning is also another alternative. We unfortunately can't do anything if the mods that are adding these biomes are removing them from their spawns.