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   4096R/ABDC4346 2019-09-12 [expires: 2021-09-11]
      Key fingerprint = 68E9 B2B0 3661 EE3C 44F7  0750 4B8E C3BA ABDC 4346
uid                  Opera Software Archive Automatic Signing Key 2019 
sub   4096R/C8B23CDB 2019-09-12 [expires: 2021-09-11]