@leocg
I cannot even launch software manager from linux menu! And when I try to reinstall/uninstall using terminal I get similar notice described in problem....

E: The package opera-stable needs to be reinstalled, but I can't find an archive for it.
E: Internal error opening cache (1). Please report.

W: Ignoring file 'signal-xenial.listsudo' in directory '/etc/apt/sources.list.d/' as it has an invalid filename extension

I am running OS Linuxmint 19.3 Mate... with opera Version:77.0.4054.146
In addition to the above which was copied from the Synaptic Manager, my software manager will not open - or uninstall/stall.. Recover was uneventful... Terminal says opera must reinstall but cannot locate an archive???
Any help or thoughts are welcome