To make the slaw, in a medium bowl, whisk together the yogurt, vinegar, sriracha, and salt. Add the cabbage and carrot and toss to combine.
In a small bowl or jar, mix together the soy, sesame, ginger, maple or honey, and red pepper flakes (if using). Set aside.
In a large skillet over medium heat, add the 1 teaspoon oil. Once hot, add white and light green parts of the scallions and cook for 2 minutes, stirring occasionally, until softened. Add the ground beef, break it up into chunks and spread it out into one even layer. Let cook undisturbed for 5 minutes (to let the beef get browned), stirring halfway through. Continue to break it up into chunks and cook until cooked through. Tilt the pan and spoon/drain off any excess fat.
Add the soy sauce mixture and cook for about 1 more minute, stirring constantly. Remove from heat and stir in half of the green parts of the scallions.
Warm your tortillas and top with the beef, slaw, avocado, kimchi, scallions, and sesame.