Unfortunately I recorded a video where my background words appear back to front when I upload it to Premier Rush, so I would love to know how I can flip the video so that the words appear left to right again.
This is not a 180 flip clock or anticlockwise, but a flip through the north-south axis from east to west.
In the Desktop app, select the clip, click on the Crop & Rotate icon to open the Transform panel. At the bottom of the Basic section, you'll find the Horizontal Flip icon. When you click it, it'll flip the selected clip.