There aren’t precompiled export templates for visionOS yet, as we cross-compile all templates from Linux and haven’t figured out the pipeline for visionOS just yet (making good progress though).
So for now you need to compile the template from source yourself.
We’re also lacking documentation on how to compile for visionOS
But it’s basically the same as iOS, just using platform=visionos instead of platform=ios: Compiling for iOS — Godot Engine (latest) documentation in English