Presentation mode in a web scene is a powerful way of presenting 3d-content. After the february 2025-update it is even more powerful, now you can get a title and a description of what you see in the scene.
It would have been very useful to be able to embed or share a web scene in presentation mode via URL-parameters.
This is not possible. You can share a slide (add #<slide number> at the end of the url), but I have not found any way to open in presentation mode.
Bern Szukalski had a blog post on this topic. Maybe he knows?