@Metamatic Hi, what's you New Tab setting (Settings > Tabs)?
Make sure it's set to Homepage.
Otherwise it will show the Start Page which is what you're seeing.
There's also a setting in Start Page or in Quick Settings to not show the Vivaldi dial if you want a completely clean Start Page/new tab page.
Make sure to read the docs:
https://help.vivaldi.com/desktop/navigation/start-page/
https://help.vivaldi.com/desktop/appearance-customization/starting-vivaldi/