If he is close and trusts you then this might work as well for you (has for me):

Don't start discussions with a concrete (recent) topic, but focus on fundamental things: Values, hopes, fears... Strengthen their argument. Tell them how you feel and why instead of making judgements.

The topical stuff is always under attack through misinformation, social media spam and propaganda. It's far more effective to honestly nurture human connection and focusing on core values. Without the fog of BS, people can see what's happening more easily themselves.

I'm in the same boat. In my case it's especially disturbing because prior to this whole gestures broadly thing, we had nuanced debates on many topics. Now, he just dismisses everything as 'narratives' if he disagrees with it.

Sadly, it seems to be based on the propaganda style I've seen out of authoritarians in general. It doesn't hurt 'their side' to break everything down to narratives, because at the end of the day, you just have to swallow the current one and you don't have to think about it again.

In another way it seems almost like a form of burnout. Like 'fuck this, I'm settling on cognitive ease from now on'.

The only way to help these kind of people is by reactivating their critical thinking. This is only possible if you tell them something that is so absurd, that even they have to reject it. For example: „Trump is Putins father.“ „Kennedy was killed by aliens, because he wanted to land on the moon.“ „We live on the inside of a hollow world with the sun in the middle.“ „The mothership will come soon and send all humans with a chip inside their brain to Beteigeuze.“ At some point they start rejecting your outlandish ideas, because their brain simply can‘t stand that nonsense. And this is the first step in the right direction for these kind of people.

I saw an interesting interview on the subject: https://youtu.be/6Ibk5vJ-4-o?t=1678

It argues the way to engage with these people is to first understand the psychological manipulation tactics they have been subjected to. That what you should focus on is not their false beliefs, but the underlying reasons why they were vulnerable to that manipulation in the first place; and to realize that everybody can become a victim of such cults helps to empathize with them. Don't give up on your friend.

Same reason for religion. Community and a feeling of self righteousness.