Solus XFCE doesn't appear to have the Keyboard Layouts panel applet.
The repos don't seem to have said package either.
No Keyboard Layouts applet for XFCE?
On a side note, it would be nice if the plugin was included by default, as it lets the user know of their current keyboard language (given that XFCE doesn't even have OSD for layout switching)
asdhio I suggest you provide your input by making a comment on this open issue. (As you can see, there's still a lot to do for XFCE. The team is working on this stuff )