I have successfully installed https://www.w3schools.com/css/css_tooltip.asp specficially the arrow-bottom version https://www.w3schools.com/css/tryit.asp?filename=trycss_tooltip_arrow_bottom
It is working perfectly on desktop, but it does not work at all on my iphone. When you tap, nothing happens.
When I access the w3schools examples directly from the w3schools website, it works fine on the phone. When I tap on the tooltip, the tooltip appears. When I tap off the tooltip, the tooltip disappears.
But even when I just copy the out-of-the-box code, unaltered, from https://www.w3schools.com/css/tryit.asp?filename=trycss_tooltip_arrow_bottom onto a page on my server, with nothing else on the page, tapping the tool tip doesn't do anything.