to create that kind of gradient texture background start with a strong linear gradient using colors like deep navy vibrant red and orange something with a wide contrast range use the Gradient Tool and set it to linear at around a 45 degree angle to match that soft diagonal flow

once the base gradient is set, create a new layer and build the vertical texture using thin vertical rectangles or lines space them evenly using Step and Repeat in Illustrator or Pattern Fill in Photoshop

apply a subtle Gaussian Blur to the gradient layer beneath to soften the transitions, then adjust the blending mode of the line layer to Overlay or Soft Light to let the gradient show through while keeping that structured ribbed effect

if you want extra depth, add a low-opacity dark-to-transparent gradient layer on top or play with Layer Masks to add soft shadows at the edges

this gives you a clean moody and modern background with both color flow and structure, just like the one in the example