That is where I would expect it to be but I’m not getting it there as you can see. I see your screen image is from your phone. I’m using the latest version of Firefox ESR on Windows 10. I’ve tested it in Microsoft Edge on the same Windows PC and in Firefox and Safari on my iPhone and it is much the same as my screen image.
On the right hand side of your screenshot there is a column of icons. At the bottom of the column there is an icon of a person. Tap the icon of the person and the logout option appears.