If your steak is not already pre-cut, slice it into 1.5” slices with the grain. This will make it easier to slice against the grain when serving. Transfer the steak to a bowl.
In a separate bowl, combine the garlic, ginger, coconut aminos, vinegar, honey, sesame oil, fish sauce, salt and pepper. Whisk until combined. Taste for seasoning and adjust with salt and pepper as desired – it should taste a little on the salty side because it is being used as a marinade. Pour 3/4 of the marinade over the steak and reserve the rest. Toss the steak with the marinade until well coated. Cover and refrigerate 4 to 6 hours.
Add the gochujang to the reserved marinade and whisk until smooth. Taste and adjust with more gochujang as desired. Cover and refrigerate until ready to use.
Preheat the Traeger Grill to 500F. Remove the steak from the fridge and let it come to room temperature.
Transfer the steaks to the hot Traeger grill, close the grill door and cook, undisturbed, until grill marks form, around 5 minutes. If using a conventional grill, cook the steaks over direct, medium-high heat. Flip and cook the other side until the thickest part of the steaks register 135F for a medium-rare center, around 4 more minutes. Baste the top side of each steak with the reserved marinade after flipping.
Transfer the steaks to a board and let them rest for at least 8 minutes before slicing against the grain. Serve with the grilled pineapple salsa and steamed rice.