RESOLVED:  Problem solved simply enough by switching to an earlier kernel in Fedora at User Login.  Apparently my dnf update DID upgrade the kernel to 5.x.  So a quick switch back to original kernel and all is working perfectly again.
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Confirming:  Fedora 28 installed perfectly and worked great until dnf update (not upgrade).  Now the mouse is invisible in the Fedora client.  Really hoping for a solution soon.