Youtube used to have a small “3D” in the lower right of the viewer as a control to select 3D options.
May be a month ago, the 3D control disappeared and the 3D settings were embedded into the “gear” settings icon.
Overnight, the 3D control has returned.
Which means the instruction for using 3D, that I just finished writing for the description section of several of my videos are now all wrong. Arghhh.