Death metal is always going to be about riff shape. For weird prog (generally jazz fusion influenced) you get Gorguts "Obscura" and Pestilence "Spheres," maybe Atheist "Unquestionable Presence," but if the bands leave behind the riff shape language, it's no longer death metal and rapidly falls apart in my experience. There are some adjacent acts like Supuration and Voivod that are more conventionally recognizable as "proggy" but for me prog starts with King Crimson, Camel, Greenslade, Yes, Genesis, etc. and is a different animal entirely.