This has been my experience too. I kept wanting to like Vivaldi for being the only tree style tabs alternative but everytime I switched to it I encouter lags at

This has been my experience too. I kept wanting to like Vivaldi for being the only tree style tabs alternative but everytime I switched to it I encouter lags at some point. I don't remeber the history panel specifically but the thing you said about main UI thread sounds like it. Eventually I decided that tree style tabs are bad for my productivity anw then I stopped seeing the apeal of vivaldi. Atm my favourite browsers are yandex for the minimalistic UI and Edge. Both have big addressbar font which is my thing. Yandex also has an Opera root I believe, it has the "turbo" mode. Privacy wise probably both are as bad as Google Chrome.