what do you guys think about open enclosures for veiled chameleons
Do you mean with no barriers at all, or screen cages?
like none ,just a uvb light and heat lamp over a tree inside or something
That would not allow for a proper environment for the lizard in question. Chameleons require very specific environmental parameters, and if they are not met, they will not thrive and can potentially die. On top of that, an “open enclosure” (or lack of one) puts the animal at risk and is not responsible. The closest you could do is have a screen enclosure.