I recently migrated to Vivaldi despite being an avid Opera user since around 2002. Over the last few years the browser has become too much like Chrome and Opera developers too much like Google developers - implementing features without adding any abilities to disable them, adding bloat that no-one asks for and afterwards ignoring all pleas from their community, which is what made them what they are.
Yes, a banner like this is a minor thing you might say, but it's an indication of a much bigger problem with their mentality. I liked Opera specifically because it was different and more customizable than others but it has slowly become faceless just like every other major browser.
Vivaldi has turned out to be pretty great. Not the best thing ever but way better and much more customizable than Opera. I have styled it the way I want, created custom images for tiles (something Opera STILL doesn't have) and it works like a treat. Sorry to say but Opera lost one very loyal customer.