Update per notes - DMC might have activated the iPhone's Accessibility feature which displays a floating Home button, to remove the floating button it was removed by turning this feature off.
I've uninstalled the DMC app on my iPhone, but the moveable button remains on the phone screen.  The button has no functionality in it. I reinstalled the app and looked for any options I missed but I can't find a way to remove the button.
Uninstall DMC app on iPhone