Apple has clearly stated within the mouse settings on the iPad that any scrolling and gesture features of the MM 1 and the MTP 1 are not supported.
Apple has made this decision not to support 10-year old Apple input devices on their newer, compatible, mobile iOS devices.
Some basic functions of the MM 1and the MTP 1 work, but that is it!
You do not have to purchase and use the more expensive Apple MM 2 or the MTP 2.
You can choose use cheaper, iPadOS 13.4.1 compatible, third party mice and track pads, instead.
You have other alternative input devices available that may work.