@BINNE this has been brought up a lot and even had pinned posts on it. The long and short of it is that:
It’s going to happen every once in a while. Generally keeping Brave updated and perhaps checking brave://components for updates can work.
You should use as few extensions as possible. Some extensions can trigger detection, such as people who have used tools like Enhancer For YouTube
Sometimes you need to clear cookies/cache because they have something saved to identify
Always good to check Shields settings. Good to have Aggressive for ad blocking and to have Fanboy’s Annoyances + uBO Annoyances enabled under Content Filtering.
Similar topics/answers on this:
Obviously the list goes on. And you’ll see even uBlock Origin and others have tons of information and topics on it. In other words, it’s not a Brave only thing: