It's an Apple system change for iPads in iOS18. It's replaced by the bar that's covering the search bar up top.

You can see a bunch of frustration from developers when this change was released here: https://forums.developer.apple.com/forums/thread/756652

Someone posted some code in there that I tried out — after trying a million other things — and it worked so that top bar will be gone, and the bottom one will be back, in v1.16! 🥳