In a medium bowl, whisk together the flour, arrowroot (or cornstarch), salt, cayenne, white pepper, onion powder, garlic powder, paprika, Old Bay, and nutritional yeast until evenly combined.
In a separate bowl, whisk the hot sauce, non-dairy milk, and Dijon mustard until smooth to create the wet batter.
Heat the vegetable oil in a large Dutch oven or deep pot over medium heat until it reaches 350°F (use a candy or deep-fry thermometer to monitor).
Prepare a baking sheet or plate lined with at least two layers of paper towels and set aside for draining the fried cauliflower.
Working with one floret at a time, use one hand to dip the cauliflower into the wet batter, then transfer it to the dry flour mixture and use your other hand to coat completely.
Repeat the dredging process a second time for each floret: dip again in the wet batter and then coat in the dry mixture; place dredged florets on a parchment-lined baking sheet as you go.
Carefully add enough florets to the hot oil so they are fully submerged but not crowded, and fry for about 4–5 minutes, turning gently until golden and crisp.
Using a spider or slotted spoon, transfer the fried cauliflower to the paper towel-lined baking sheet to drain.
Allow the oil to return to 350°F between batches, then continue frying the remaining florets in the same manner.
Serve the fried cauliflower hot with your favorite dipping sauces.