Can text within an iframe be copied to clipboard?

As mentioned here:

To use the API in iframes, you need to enable it with Permissions Policy, which defines a mechanism that allows for selectively enabling and disabling various browser features and APIs. Concretely, you need to pass either or both of clipboard-read or clipboard-write, depending on the needs of your app.

<iframe src="index.html" allow="clipboard-read; clipboard-write"></iframe>

If you only want to be able to copy text to the clipboard (i.e. you don’t need to be able to read the clipboard programmatically), then you only need the clipboard-write permission:

<iframe src="index.html" allow="clipboard-write"></iframe>