In amber read me there's an example at the bottom.
In this note from nostr:npub1ye5ptcxfyyxl5vjvdjar2ua3f0hynkjzpx552mu5snj3qmx5pzjscpknpr there's the code he uses in nostrudel
Discussion
It's not working with Mull (firefox fork for android), only with chromium browsers. I think it's related to clipboard permissions