I think it is like this:
-permitephemeral=send,dust,anchor
Relay transaction packages that include ephemeral outputs defined by comma-separated options (prefix each by '-' to force off): "anchor" to allow minimal anyone-can-spend anchors, "send" to allow ordinary output types to be considered ephemeral, and "dust" to allow for dust-amount outputs rather than strictly zero-value (default: %s)", "anchor,-send,-dust"