Comment 6 for bug 790980

I recently switched to KDE 5.16.2 on Manjaro and ran into the same issue. My research suggests that KDE forces a fixed (or maximum) height/width for AppIndicators and is unable to render the icon produced by this indicator.

The indicator itself works, as the context menu appears and you can see the graphs being produced in /run/user/1000/multiload-icons-*/

I tried an applet from a similar project, multiload-ng, which has the same issue.
https://udda.github.io/multiload-ng/

However, the "systray" version of multiload-ng and it works, although it lacks the context menu of indicator-multiload, which I really liked! I did try [indicator-multiload --trayicon] to load the 'systray' version of the indicator, but it yields the same result. I think multiload-ng works as it creates multiple 'tray icons' and lets the desktop environment handle the size/order, which might be a workaround for this indicator to display under KDE.