Comment 7 for bug 1775526

I had this issue as well when running anything dpkg related in the terminal, the "blindly entering your password" trick did not work for me, but I did find a fix.

Running the software updater completely fixed the issue. It actually came with a popup for the password, which seems to be the missing link that #4 is talking about, but pressing enter after adding passwords in it did not work for me, I had to press next, which explains why typing passwords and spamming enter did nothing.