The one available to download from the app hub (https://www.opera.com/pcappshub/adobeflashplayer) is for an older version, which means that it cancels the installation and directs you to download a newer version. The problem is that downloading from Adobe's site (https://get.adobe.com/flashplayer) doesn't work because instead of the install button, it shows this note:
"Your antivirus software must allow you to install software."
However, I've concluded that it isn't any antivirus software or anything else blocking it, but Opera. Anybody got suggestions that doesn't include downloading Chrome? Both "can't get rid of these" Microsoft browsers have Flash built in and redirects to the help page.