Copy and paste in Facebook is pretty much similar on the mobile device, the only difference is a way of selecting and pasting the text or image.
In mobile, the selection is done by holding the text for 2-3 seconds and then dragging the content selection. Pasting is also the same you just need to tap and hold the text area and wait for the popup to paste the content.
Read more: https://ityug247.com/how-to-copy-and-paste-on-facebook/
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