@gianlucagiardina2
In first post you told that you had problems on Windows - now you say that on Windows all worked well.
On Ubuntu I have no experience at all, sorry. Do other Ubuntu browsers see and use your CA there?
Hello. Nice to meet you. It worked. Thank you. I was not sure if addon extensions from Google [Chrome] worked in Opera. I see they do! I see Checker Plus for Gmail and Gmail Checker Lite also work as well.
Logging into Gmail requires oAuth2 support now that Opera Mail doesn't support. However, someone said that if you goto https://myaccount.google.com/security, enable 2-step verification, create an app password for Opera Mail and use that app password to log into your Gmail account in Opera Mail, things will still work. You'll have to test.
@kirill1996 maybe because you don't have at least Windows 11, needed to install Opera from version 96?
Or maybe you have downloaded an old offline installer?
The problem was that I could not access the files from under the new account to the Opera folder on the other partition of the drive.
Got full access to the folder and updated offline with the installer with no problem.