Manually adding the Opera RPM repository

Installing signing key

sudo rpm --import https://rpm.opera.com/rpmrepo.key

Fedora Instructions

sudo tee /etc/yum.repos.d/opera.repo <<RPMREPO
[opera]
name=Opera packages
type=rpm-md
baseurl=https://rpm.opera.com/rpm
gpgcheck=1
gpgkey=https://rpm.opera.com/rpmrepo.key
enabled=1
RPMREPO

sudo dnf install opera-developer

OpenSUSE Instructions

sudo tee /etc/zypp/repos.d/opera.repo <<RPMREPO
[opera]
name=Opera packages
type=rpm-md
baseurl=https://rpm.opera.com/rpm
gpgcheck=1
gpgkey=https://rpm.opera.com/rpmrepo.key
enabled=1
autorefresh=1
keeppackages=0
RPMREPO

sudo zypper in opera-developer

The GPG fingerprint

For your reference, the fingerprint of the current GPG key is:

2019 key

pub   rsa4096 2021-06-23 [SC] [expires: 2023-06-23]
      9FBDE02F55F254D700821CCCDD3C368A8DE1B7A0
uid           [ultimate] Opera Software Archive Automatic Signing Key 2021 
sub   rsa4096 2021-06-23 [E] [expires: 2023-06-23]