I think that adding email clients to the sidebar in Opera and Opera GX would greatly reduce time to open a new tab and closing it later, without seeing the website/page you are currently in. I would recommend Gmail, Outlook live (formerly Hotmail), Yahoo mail, Mail.com, etc.
I've fixed it. Downloading the media pack from the site didn't work but I went to "Settings> Apps> Apps & Features> Optional Features> Add features", searched "Media Feature Pack", downloaded it from there and it seems to have fixed the issue. Thanks for the help!
@atramedes Because Opera never felt the need to add it? Because Start Page never wanted to be there? Because Opera and Start Page never reached an agreement? There could be lots of reasons.
@JoeBejm Those who create GX decided that it should have only a dark theme, what makes sense in my opinion.
There are some topics asking for a light theme, you can hsow your support for it in one of them.