@davidrmf - in version 71.0.3770.271 turning on hardware acceleration terminates the bizarre behavior of no apparent right mouse click and so forth.

@KetoKelo - fixed it for me, thanks KetoKelo!

@leocg Deleting my ~/.config/opera folder did not get rid of the blank Settings page. I have switched to Opera developer and got rid of Opera-stable via "apt purge --autoremove opera-stable". If I'm inclined to try Opera stable again I'll download it. Fresh start.

@jimunderscorep Thank you. I'll reset it. Re-customizing it will be irritating. As for bookmarks, Bookmarks Import & Export by Martin Sermak is an extension for Opera. I find that it works, although the Export and Import processes ignore nested folders, so nested folders are flattened and saved as regular folders.
https://addons.opera.com/en/extensions/details/bookmarks-import-export/

Better address bar disappeared from flags, but typing lagged anyway, so I disabled pretty much everything in flags. This ended the typing lag, but now I get a blank page for settings. I tried uninstalling and reinstalling Opera, but I still am denied access to settings - also bookmarks. Is there a way in Linux Mint 18.3 to get up to date Opera to forget it has ever been installed?

It was the ad blocker - thank you l33t4opera!

WCRB - classical radio Boston - streams music. This used to work in Opera, but now none of the streams will load. It says "loading" forever, so it doesn't play. This forces me to use Chrome, where "loading" flashes by and the streams are available. Edge also loads and permits playing the music. It doesn't matter - Linux or Windows - Opera's misbehavior is the same. Probably Mac as well.

I am an idiot. Thanks for your response - of course it worked.

I'm trying to uninstall-delete-remove ADBLOCKPLUS, an extension for Opera. It is easy to to this in Chrome - you just click on the trash can to the right of the extension. That's not there in Opera. I looked around and found nothing. After deleting the extension's folder didn't work, I uninstalled and reinstalled Opera a couple of times. ADBLOCKPLUS is still there, grayed out, in extensions. Someone knows a way. I beg the one who knows to tell me how to do it. Please.

I am bitching about yet another email program's demise - the death of opera mail. Bitch bitch bitch.