yes, and repeat Vivaldi same version has no problem to log in Gmail new page from Ubuntu 20.04 . I guess the explanation is in the last of the four reasons listed when you go on the “learn more” link :
"Google might stop sign-ins from browsers that:
-Don’t support JavaScript or have JavaScript turned off
-Have unsecure or unsupported extensions added
-Are being controlled through software automation rather than a human
-Are embedded in a different application "
because the first three are not true in my case.
In Vivaldi users forum they do not have enough knowledge of this browser behaviour on FreeBSD inside a Linux emulation installation