Depends what you mean with "to select something"; for example if you click on the URL bar in Firefox then all the text is automatically selected. Should that count as the user "selecting" something? Perhaps not? None of this is very straight-forward.

If I do that in a Chrome-based browser, the text looks like it's selected, but it isn't. Same if I just mark the text using the left button. It won't paste when I click the middle button. I have to click again, then double click, and then it'll paste - most of the time.

Elsewhere I either double-click on a word, which will select that word for pasting, or I mark a section with the left button (press and hold at the beginning of the selection, move and release). And the middle button will paste. And paste again, if I wish.

But URLs in Chrome-based browsers instead behave in the annoying way described above. In the past it worked as expected.