Hi, thank you for your question and detailed info about what you tried.
Unfortunately this does not work because the USB is there only for power and firmware updating, no other functionality is implemented.
The driver chip is not capable of emulating MIDI over USB (or any other advanced modes like for example mass storage), it is merely a "virtual serial port" (similar to for example Arduino development boards and many other). Normally there is no reason to connect Gecho to any USB port other than for powering.
Unless your controller also has the classic, opto-isolated MIDI (DIN5 or 3.5mm TRS Jack) output, you'll need a USB host. The host is meant for connecting a MIDI controller, it translates data from a USB MIDI device into the 2-wire MIDI signal.
By "USB host" I mean something like this:
https://www.aliexpress.com/item/4001202281136.html NOT this, as this cable has the opposite purpose:
https://www.aliexpress.com/item/1005002736754622.htmlThese are just examples, I haven't tested any particular one - soldered mine from these modules:
https://www.hobbytronics.co.uk/usb-host-board-v24https://www.hobbytronics.co.uk/midi-breakoutW10 does not seem to 'recognize' the Loopsynth (no sign under devices that it is plugged in) - I read somewhere that a driver would be needed? If yes, where, which?
There are drivers but they are only needed for firmware updating / development. In theory a driver could be written that acts as a "virtual USB host" and creates virtual MIDI instrument in Windows, to integrate with various software or even to make the PC a host for external hardware controller, but writing such driver is beyond my knowledge.