Unfortunate. What will he play under then? The FIDE flag?
Feel a bit bad for Nepo

Unfortunate. What will he play under then? The FIDE flag?
Probably No flag at all

What does the WADA have to do with chess??? Seems unfair imo
Read the article. It does have to do with it

Why can't he play under the Russian flag?
Because there's a ban on Russia by WADA that would last until around 2022

everyone loves to and has a desire to represent their country in a big event
Everyone? Perhaps an overstatement. How much so? Who knows. More importantly, what does Nepo think?
It was at the Candidates semi in 1977 Korchnoi asked to play with the Dutch flag but this was vetoed by the Soviets on the ground that he had lived there less than a year after his defection. It was Korchnoi’s seconds who then suggested the Jolly Roger but this too was vetoed and in the end he played without a flag. Polugaevsky also refused to shake hands for the first games. None of this had much effect on Korchnoi, who was 5-0 up in wins already after 7 games...

It was at the Candidates semi in 1977 Korchnoi asked to play with the Dutch flag but this was vetoed by the Soviets on the ground that he had lived there less than a year after his defection. It was Korchnoi’s seconds who then suggested the Jolly Roger but this too was vetoed and in the end he played without a flag. Polugaevsky also refused to shake hands for the first games. None of this had much effect on Korchnoi, who was 5-0 up in wins already after 7 games...
I bet it had some effect on Polugaevsky though.

I don't think he'll lose sleep over it. he'll probably play under a fide flag just like firouzja has.

There was a big incident in checkers this week (by no means the trivial game that many chess players seem to think) where a Russian played under a Russian flag.
Russia is still serving an International sporting ban for hiding drug usage so it comes back to the old "Is Chess/Checkers a sport" question.
Ian Nepomniatchi won't be able to play under the Russian flag in the world championship match against Magnus Carlsen.
This isn't much big of a deal and is not going to impact the game in any way whatsoever , but everyone loves to and has a desire to represent their country in a big event , which Ian would not be able to unfortunately.
To know more
https://www.chess.com/news/view/nepomniachtchi-russian-flag-wada-ban