Found this documentary - it was made about a decade before the pandemic, but...
No further comment.
(Video: 35 second, fair-use clip, no audio)
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Okay, a little more comment...
It's a documentary about a huge traditional music festival or choral festival or something like that in Estonia.
To Breathe As One (2009)
@Pat Ha, my guess was right. I was thinking 'Is that an Estonian flag?' and was about to check it out. :)