My experience: DuckDuckGo is my default search engine. It appears the problem to which I replied is entirely attributable to Brave’s new Enable De-AMP flag. Whether / how / if the De-AMP flag relates to tabs (the apparent subject of this thread) — I don’t know.
edit — Also my experience: I’m extremely cautious about toggling flags to other than the default. If you do change the Enable De-AMP flag (or any other flag), keep a record of your change(s) so you can later revert to the default.