Emojis do not show up in Artistic Text. I tried with Helvetica, which is a Unicode font and should work for that, shouldn't it? However, I also tried with the Emoji font itself and also the "Pictographs" from macOS "Show Emoji & Symbols", the pictographs are partially showing up correct but not all of them.
Please see attached video.
All the best,
Roland
Affinity_Designer_171_Emoji_Artistic_Text.mov