I am using adaptable which I downloaded less than a week ago while upgrading to 3.5 and I am now experiencing this issue. Atto drop-downs work in clean but not adaptable.
After inspecting each of the files mentioned in https://bitbucket.org/covuni/moodle-theme_adaptable/issues/909/atto-drop-down-menu it looks as though my files have all the latest changes however the Atto dropdowns still do not work.
The language submenu was already disabled, so that isn't the issue.
Any thoughts?