I can't remove Opera from my Mac, it's not showing in the Apps folder

Under Normal operations all Applications installed on the computer are placed in the Applications folder and this would include Opera.

Where exactly on the computer does this issue alert the user that Opera is Installed and therefore needing removal

Do Not Install any Uninstaller Application as they tend to remove elements of the Operating System files and may render the computer unstable and may even require a Reinstallation ?

Malware and Adware is often time downloaded and installed by the use downloading from Untrusted Website who bundle the malware and adware into their package.

For that specific issue or suspect being infected with Adware / Malware >>

There are no known Windows-like Viruses in the wild that self replicate and affect macOS, because of the underling UNIX  Foundation and Permission Limitation. 

The The Built in Security  is all that is required to protect the computer.

Should “ Certain & Specific Software “ referenced from above be installed - it will negatively impact macOS. It is suggested, to download directly from a respected ASC Contributor, the application Malwarebytes for Mac. 

It is free or paid for added features. 

Disclaimer: I am not affiliated with nor receive compensation from the Developer.

Run the Application and it should remove the malware / adware. Once done, restart computer and test.

Safe Boot, (holding Shift key down at startup), does the problem occur in Safe Mode? Could take 10 minutes.

Safe mode attempts to repair Disks & clears lots of caches & loads safe Drivers, & prevents loading of 3rd party extensions, so if Safe Mode works try again in regular boot.

EtreCheck is a FREE simple little diagnostic tool to display the important details of your system configuration and allow you to copy that information to the Clipboard. It is meant to be used with Apple Support Communities to help people help you with your Mac. It will not display any personal info.

https://www.etrecheck.com/

Pastebin is a good place to paste the whole report if you capture the URL while there…

https://pastebin.com/

Whew, they've changed pastebin & made it harder, but after pasting in, click Create new paste button, then Embed button, then copy the URL...

<script src="https://pastebin.com/embed_js/KuvnghqA"></script>

The important part of the above is between the quote marks...

https://pastebin.com/embed_js/KuvnghqA

If pastebin is a problem for you then workable but harder for me to work with...the Note tool on the bottom of this editor's toolbar, as shown in the image, to copy and paste the output from EtreCheck. In a Reply before you click post, look for this to add longer texts...

Hasenfb wrote:

Is there a program or some anti-malware that can remove Opera? It's such a pain!

If you can't find it in the normal Applications folder, note also that each user has their own Applications folder inside each User's home directory. Normally, as P. Phillips points out, the computer-wide Applications folder is where you install applications like Opera. To check if it somehow was installed into one of those User-specific Applications folders, log in as each user in turn and look in the Applications folders that are inside each User's home directory.