System Workbench for STM32

Serial and parallel connections are fairly simple using the STM32 Cube settings and libraries for UART or FSMC (parallel port) wizards. I won't go into those.
You don't need a USB stack specifically for the printer class since you can use the STM32 Cube USB Host CDC (serial communications host) example for that.

This is the serial communications host application. You can set dummy baud rate settings which would not apply, and instead of your data connecting to an upstream serial port, just connect the data buffers to your MCU application.

When the printer is plugged in, wait for USBH_Get_App_State to equal APPLICATION_READY, and then just use the USBH_PTC_Receive() and USBH_PTC_Transmit() functions with their respective call-backs to receive and send buffers of data to your USB printer. Yes, it is that simple.

You can verify the enumeration and class of your printer from the structure “USBH_HandleTypeDef *phost” if you want to, but if this is an embedded application, you can probably ignore all of that, and it works automatically to connect even if the printer is not a “CDC” device.

Joe