I pay for Brave Search Premium, but can't use it

I’m paying for Brave Search Premium subscription and it works in Brave browser, but for now I use Vivaldi and when I verify my email and complete the redirection procedure back to search - it asks me to try Premium again. Is this by design? Shouldn’t search be independent from the browser and just work for me if I pay for the service? I don’t remember that somewhere there were terms specifying that Premium works only in Brave. Can you recheck, maybe it’s a bug?
I want to support the company, but I also want to use it legally without ads, for example.

PS rechecked in Google Chrome - same picture, shows that my account is activated, but not working in actual search UI.

At this time, Premium features can only be used in the browser.