Return the pan to medium high heat and add in the cut up bacon strips. Fry, stirring frequently, until the bacon is beginning to crisp and has rendered at least 1 1/2 tablespoons of fat, about 4 minutes.
Stir in the onions (and chopped greens stems, if using). Fry for about 4 more minutes, or until the onions are translucent, tender, and starting to turn golden.
Add in the sliced garlic, smoked paprika, crushed red pepper flakes, kosher salt, black pepper, and dried thyme. Stir for 1 minute, or until fragrant.
Add about 1/3 of the greens and use tongs or two wooden spoons to toss with the hot onion and bacon mixture until the greens wilt, turn bright, and shrink a bit. (If you're starting with dry greens, see Cook's Notes). Repeat this until all of the greens are incorporated into the pan.
Add the chicken stock and vinegar, stir, and bring to a simmer. Simmer until the greens and stems reach your desired level of tenderness; for us, that's about 5 minutes.
Finally, add the drained and rinsed beans to the mixture and toss. Continue cooking just until the beans are heated through.