On the basic settings page, gx settings the last option is also "Force dark pages". Turn this off and go to https://web.whatsapp.com you will be able to login and then just open the sidebar one, it will ask you if you want to transfer.
@mastadonta In Google settings you can define if pages will be opened in a new tab or not when you click on a link in the search results.
Opera doesn't have a setting to override the sites decision about if links will be opened in the same tab or not. However, you can use, for example, middle click to open a link in a new tab.
@leocg I have an IT department monitor this PC and they looked into all of that and said it all seemed normal and it should be on the browser side. Other browsers work fine.
May be worth noting I also uninstalled and reinstalled and restarted the computer multiple times. Still is in this constant loop of loading something in the background.