It's been a few tears... Any updates?
I'm working for a company doing "die cut" stickers. We get in random art from customers... PNG w/transparency, Illustrator, Photoshop files, JPGs.
I open most in Photoshop, resize, remove backgrounds to transparent and create a solid black mask to generate the die line from. Auto trace in Illustrator, then offset path to give a little extra sticker around the art. Also use Mimaki Fine Cut plug-in to generate the offset line too, after tracing in Illustrator. Then I "simplify" the dieline and adjust for the cutters that don't like pointy stuff, hangs up the blade. They print on a Mimaki UV Inkjet/cutter combo and have a separate cutting machine too.
Just got a new PC and all the updated software and tried working in Affinity, the autotrace was the dead end... ;-(
Tried some of the alternative tracers mentioned here, not so hot.