Just to tag on, the only real “widespread” (read: more than a few freak cases of something I haven’t heard about) issue was specifically Vitamin E Acetate in black market illegally produced THC vape carts (sources vary whether the carts were either from China or from some midwesterner’s kitchens.)

You’re correct there has never been a case of popcorn lung due to vaping, the only recorded cases I’m aware of involved a popcorn manufacturing plant using a powdered version with no respirators, and from what I understand it basically works like butter flavored mesothelioma (the powder settles in lungs and doesn’t get exhaled, which doesn’t happen if it’s not powdered, or if you use respirators…I think.) In any case, there also will never be a case of popcorn lung from vaping, and I say this because there’s never been a case of popcorn lung from smoking cigarettes which coincidentally happen to contain 2,000x the amount of diacetyl as vape juice ever did (and that’s before vapes largely stopped using it due to the propaganda on it, which was spread by big tobacco and big pharma to boost their cigarettes and chantix sales btw.)

I vaped at the time and had to rant this shit at some old guy who was holding a cig at the bar saying “ooohhh popcorn lung” at the bar, like “shut up and drink your Bud there, COPDeez nuts.”