There are also other solutions that provide Microdrive hardware emulation:

ZXPicoMD

This project by Tom Dalby offers a Microdrive emulator for the Sinclair ZX Spectrum, based on a RaspberryPi Pico. It uses an SD-card for cartridge storage, and an OLED display + hardware buttons for user interaction with the device. The hardware design is offered under an open source license, the software is closed source, but partly documented.

vDrive ZX and vDrive QL

These two hardware emulators for Sinclair ZX Spectrum and Sinclair QL are sold by vRetro Design. They use SD-cards as storage media and are controlled via toolkit software to be loaded onto the Spectrum/QL. Hardware design and software are closed source.