Firefox is extremely annoying using Hubs in fullscreen. Open a tab, type about:config as location, and set:
full-screen-api.warning.timeout: 0
pointer-lock-api.warning.timeout: 0
This time I did the tutorial for Spoke—which you should absolutely sit thru, and try out as you go—and then made a scene based on the Material Test. Well, first I tried to edit the cafe, but it turns out that's a single model with 80K polys, not editable. Pity.
So you can make a scene by adding items from a library, Architecture Kit has most of the building blocks you'd want, mostly in 1x1 to 4x4m segments, and a small palette of industrial textures.
Google Poly and Sketchfab have hundreds/thousands of items to drop in.
Unfortunately, while you can upload your own textures, you can't put them on any object, they're just images. The best I've found for now is to just lay it down like a carpet, 0.01 above a flat surface so there's no z-fighting. Works but obviously stupid. The actual workflow is apparently to clone ArchitectureKit, edit it in Blender (oh fuck), upload.
Not a bad toybox, not as good as Second Life, Garry's Mod, or Unity, but usable, and a lot cheaper (paying SL $1 per 25 images sucked giant balls until later I made it back 1000x by selling things and coding services).
The Spoke controls continue to be awkward, and often contradictory to Hub's, but I got used to them.
There doesn't seem to be any way to select or group multiple objects and apply changes to all of them, except translation, rotation, etc.; texture remapping is kind of a pain. And there's no texture offset field, so if your objects aren't full-sized and don't line up exactly, you can't make them fit. Don't use hex or tile patterns on such objects, I guess, or hide the seams under carpets.
After a bit of work, mostly changing textures but adding some trim, adding a doorknob, fixing misaligned blocks, I got a slightly better version of their demo, hit Cmd-S to save (in Spoke), then Publish to Hub. Which takes >1 minute for a tiny default scene.
So starting over from the watery caldera template, and a "forest" model from Poly, I'm building up a dark twilight castle, we'll see how that goes.