The skeleton horse does not count towards monster hunter, or monsters hunted, but the zombie horse and zombie nautilus do.
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Comments 2
Hi!
Thank you for your report!
However this works as intendent.
We're already resolved this issue at MC-303546, so I will resolve and link this ticket as a Duplicate.
I suggest also to browse through the main issue for potential fixes.
Quick Links:
📓 Issue Guidelines – 💬 Mojang Support – 📧 Suggestions – 📖 Minecraft Wiki
Or the Best Friends Forever advancement.