I disabled DuckDuckGo Privacy Essentials on Firefox and it fixed the problem for me - thanks very much for the tip.
(Disabling DDG on Vivaldi didn't help, but maybe Vivaldi is natively doing whatever DDG does that causes the problem. I tried disabling all my extensions on Vivaldi and the problem remained.)
(Disabling DDG on Vivaldi didn't help, but maybe Vivaldi is natively doing whatever DDG does that causes the problem. I tried disabling all my extensions on Vivaldi and the problem remained.)