Set your Instant Pot to "Sauté" mode. Add the vegetable oil and heat it.
Add the minced garlic and ginger, and sauté for about 30 seconds until fragrant.
If using tofu, add the cubed tofu and cook until lightly browned on all sides. Remove tofu and set it aside.
Add all the prepared vegetables to the Instant Pot and stir-fry for 2-3 minutes.
In a bowl, whisk together the soy sauce, thyme, oregano, rice vinegar, maple syrup, and cornstarch until well combined.
Pour the sauce mixture over the vegetables in the Instant Pot. Add back the tofu if using.
Close the Instant Pot lid, set it to "Manual" or "Pressure Cook" mode, and cook on high pressure for 0 minutes (yes, zero minutes).
Quick-release the pressure when done, and carefully open the lid.
Stir the stir-fry, allowing the sauce to thicken. If it's not thick enough, you can set the Instant Pot to "Sauté" mode and stir until the sauce reaches your desired consistency.
Serve the dairy-free stir-fry over cooked rice or noodles. Garnish with sesame seeds and sliced green onions if desired.