There are few other possible workarounds
1.I can’t really test it on iPad, but even chrome on android presented the same issue for me,
A Textarea workaround seem to work on it, if thereported behavior in the link below is correct on iPad as well, then using the textarea trick could work on mobile safari too.
Will Code For Equity - Blog - Mobile Safari Ignores textarea readonly Attribute
You can also try and test it pasting this executable url in the address bar of your device
open a topic
paste the following in the address bar
scroll to the bottom topic share button
you will see the share box open and the input should be selected and and selectable
I tested the following on my N4 and allowed me to select and copy, but copy button UI was not triggered by this code.
instead of the css approach