I have also been experiencing drop down issues when using my site in standalone mode (added to homescreen). I am running iOS 15.3.1. Most of the time, the drop downs work, but occasionally, when you click on a drop down, nothing appears to happen. But if you click on where it would be, then it actually updates the selection. Sometimes, you can see the drop down, but it is very faint, and smaller than normal. The faint drop downs can also follow you across the site. You can see a faint bar. It is very strange. The only way to fix it, is to kill it, and re-open it. Then everything works fine again. My site is not using any JS frameworks. Just pure HTML with the occasional jQuery plugin like "chosen". I am now getting emails from members of my site. They ask me why they can't update certain drop downs. This is becoming a huge issue.

I was really hoping it would be fixed in iOS 16.0 but it seems to be as bad as ever. Come on Apple!!