I just had a thought, I tried this on my iPhone and it seems to be okay, although I didn’t do a full round of tests.
In your browser options there should be a setting that says, “request desktop site.” click on that and it should refresh the page after a moment. If not then manually refresh it and you should see the desktop version, which will be wonky on a phone screen but will also get the functionality to accomplish the task. Scroll to the bottom and sort of hold/tap on a chat tab. Then the X should be just to the right. HTH