So it looks like glass itself is still safe, with a caveat that I did not think of, because it looks like an alarming number of these glass products apply paints and glazes that contain heavy metals, which are definitely not safe. I would probably do some more research about the brands that make these products and find out which ones you can confirm are not applying toxic coatings to their glass.

My take is the glass tumbler is safe as long as its just a glass tumbler with nothing else - basic borosilicate glass is chemically inert if it is 100% uncoated, uncontaminated borosilicate glass. Which is why chemistry experiments are always done in glass, it doesn't get any more inert than that

And no, lead crystal glass is not safe, but that stuff is usually really old and decorative, its also extremely heavy, and generally called 'crystal' rather than glass, even though as the author of that piece points out, it is technically a glass, though I've never seen it labeled like this