In a small bowl, combine rice vinegar, 1 tablespoon sugar, and 1/2 teaspoon salt. Add julienned daikon and carrot, toss to combine, and set aside to pickle while the brisket cooks. Stir occasionally.

Season brisket generously with salt. Set Instant Pot to Saute on high. When hot, add brisket fat-side down and sear 4-5 minutes until deeply browned. Flip and sear the other side 3-4 minutes. Transfer to a plate.

Add ginger, garlic, star anise, and cinnamon to the pot. Saute 1 minute until fragrant. Pour in beef broth and scrape up any browned bits. Stir in fish sauce, soy sauce, and brown sugar until dissolved.

Return brisket to pot, fat-side up, nestling it into the liquid. Seal lid and cook on High Pressure for 60 minutes. Let pressure release naturally for 15 minutes, then quick-release any remaining pressure.

Transfer brisket to a cutting board and tent with foil. Remove star anise and cinnamon. Set pot to Saute and simmer the liquid 8-10 minutes until reduced by half and syrupy. Skim excess fat if needed.

Slice brisket against the grain into 1/2-inch thick pieces, then shred with two forks. Return to the reduced sauce and toss to coat. The meat should be tender enough to fall apart easily.

Pile brisket onto warm tortillas. Top with drained quick pickles, cilantro, and jalapeno if using. Serve with lime wedges for squeezing over top.