Originally Posted by llewellen

@BW-userx: I figured out the problem. Recall that I downloaded and installed two packages from AUR: Vivaldi itself and also a separate package of additional codecs. I know from previous that Vivaldi does not include some proprietary codecs that are necessary for some video streaming.

I removed the codec package, re-intalled Vivaldi, restarted and voila - Vivaldi is running fine.

This begs the question of how I was previously able to install Vivaldi and the codecs and I think there may be two alternate answers: either the codec package that I most recently installed had been upgraded to require GLIBC_2.27 or else I had previously installed a different codec package. I know that I did install some codec package because Vivaldi wouldn't play a particular site that I wanted but after some advice I installed codecs and it did play. I'll continue to investigate this aspect.

Thank you for sticking with me and for your advice.