Not my project, but another approach recently published used Depth Anywhere to create a virtual depthmap for a given 360º equirectangular image and then apply to point cloud and render using three.js / A-Frame.

Appears to be similar capability as OP for creating scene depth from 2D, but using point cloud instead of gaussian splatting for rendering so looks more pixelated: https://github.com/akbartus/360-Depth-in-WebXR

Also unlike the World Lab example you have the ability to go further outside the bounds of the point cloud to inspect the deficiencies of the approach. It's getting there but still needs work.