Apple is working on a granted patents for technology that could be used in such devices.
Apple's Foldable iPhone Could Sport 5.49-Inch Cover Display 6e2k3j
In a Oppo Find N series, while sporting a shorter and thicker build. The says that Apple will equip its folding phone with a 5.49-inch cover display, which also happens to be the same size as the outer screen on Oppo's first generation Find N handset.

Photo Credit: Screenshot/ Weibo
On the inside, the foldable iPhone will sport a 7.74-inch screen, the tipster says, adding that the larger display "unfolds like [an] iPad" which should offer a larger display for viewing content. The foldable is also said to have an "unprecedented screen ratio or aspect ratio.
According to Digital Chat Station, Apple's rumoured foldable could be positioned as a device that offers smartphone and tablet functionality. If Apple were to launch such a handset, it would compete with other book-style foldables, such as Oppo's Find N series, Samsung's Galaxy Z Fold lineup.
Earlier this month, another tipster suggested that Apple's first foldable phone could be launched report states that Apple has secured an ultra-thin glass supplier for an foldable device.
On the other hand, Bloomberg's Mark Gurman previously claimed that the company is working on an iPad-like foldable that would not feature a visible crease. According to the reporter, this device could be introduced in 2028. Apple has yet to announce any plans to launch a foldable device, but we can expect to hear more about any rumoured devices in the coming months.