How do I deal with my friend who believes in chem trails?

Not only have I been in this situation, I have been the chemtrails person. I wasted so much of my life on those rabbit holes and I wish I'd put my time in to proper education instead of "doing my own research" on youtube and forums. In the late '00s I would take pictures of them all the time and on I have a large folder on an old drive full of criss-crossed skies lol. Always looking at the sky and feeling despair at the amount of chemtrails up there. Wondering what they were spreading in the clouds and feeling like there's no hope for humanity because we're being forced to breathe in whatever it was. What pulled me out of it, ironically, was watching a Joe Rogan podcast at the time, where he made the point that the true controvery should be that jet fuel destroying the planet, and while everyone worries about the chem trails, they're missing the point. I guess the reason it worked is because Rogan had pointed out another type of cover up, so my brain latched on to that one instead. People often fall in to these beliefs when they are dealing with big upsetting or stressful events. Even things you might not see from outside, like questioning their own mortality. It can start as simply as "This cant be all there is!", and before you know it you're down a pseudo-scientific rabbit hole, being told that they're dropping nano-tech on the population to control our thoughts. My advice to you would be to understand that arguing will not bring him out of it, so don't bother. Conspiracy believers must come to their own understanding. You could plant the off seed here and there. You could leave educational material around, or, if you understand anything about aviation you could explain what you know. But they will likely find ways to push back and develop further theories in their mind about what you tell them. You don't have to listen to it either. If you've told your friend that you're not a believer in chem trails, and that you want to talk about something else, and they still keep bringing it up, then it's fine to build a boundary there for your own sanity and peace.