I know we aren’t allowed to use Chrome.
Who says? Use whatever you want, if you want to use Chrome then use it, nobody is stopping you.
As for Vivaldi, I personally think it's the best Chromium browser out there, highly customizable with all the good stuff from old Opera without none of the garbage from current Opera, plus it seems to be reasonably respectful of your privacy. Their only mistake was building it on Chromium.