New iPad Pro 11" not recognizing USB Midi

Perhaps you refer the Apple USB-C to USB Adapter?

https://store.apple.com/uk/xc/product/MJ1M2ZM/A

While this adapter can be used to connect basic USB devices to your iPad’s USB-C port, it is perhaps not an appropriate solution for your need. Also consider that you’ll not be able to charge the iPad while using this adapter with connected devices, whereas a USB-C hub provides opportunity to simultaneously connect USB devices of almost any type - and charge the iPad and power the USB devices via USB PD (Power Delivery).

The iPad USB-C port is considerably more capable than basic USB. Using the correct USB hub for connections is not a backward step, but is instead an enabler. In acquiring your iPad M2, you have a very powerful device; attempting to hobble the iPad with old USB technology, instead of using appropriate connections, will introduce unnecessary complications and difficulties.

By your own admission, your existing hubs are unsuitable for your current need. Investing in a modestly priced USB-C hub, to replace older [now] incompatible technology, needn’t add bulk or unnecessary complication. Using an appropriate USB-C hub will both address your current problem - and will allow you to exploit the advanced capabilities of your flagship iPad Pro.

You’ll not be able to use a USB Type-A to USB-C cable to connect your iPad Pro M2 to a standard USB Hub. This arrangement won’t work.

Without delving into the intricacies and technicalities of USB bus-topologies, requiring more explanation than there is room for reply, perhaps conceptualise USB Type-A as being a directional cable. The Type-A plug always connects to the control-end (the computer), while the associated Type-B plug connects to the device being controlled. While USB-C can be bi-directional, if the cable has a Type-A connector at one end, the directional concept applies. You’ll not encounter USB Type-A to Type-A, or Type-B to Type-B cables.

To use your new iPad for your described application, you will need to replace your existing USB Hub. You will require a hub that accepts a USB-C host connection (many USB-C hubs have a USB-C pigtail connection with which to connect the host computer - here, your iPad). To the hub, you will connect all your other devices.

There are many USB Hubs that have a USB-C connection for iPad plus a USB-C PD (Power Delivery) pass-through power connector to which you can connect your USB-C Power Adapter - along with the hub itself incorporating a combination of additional USB-C ports, USB 2.0/3.1 Type-A ports, Ethernet LAN, HDMI, VGA, SD and microSD card-readers.

Perhaps consider Kingston, Anker, Hyperdrive and Satechi - although there are many others from which to choose. A Google Search for USB-C Hubs compatible with iPad will find a number of articles and recommendations. 

Speaking of personal experience, the Kingston Nucleum has proven itself to be particularly flexible for connection of additional USB devices - featuring twin USB3.1 Type-A, downstream USB-C and SD/microSD card slots, HDMI, plus a power pass-through USB-C port that can accept +45W from a suitable USB power source.