This firmware is quite old... Anyway about the Gotek- HxC all is there (files + updates) :
https://hxc2001.com/download/floppy_drive_emulator/HXCFEUSB_HFE_beta_firmware.zip
https://hxc2001.com/download/floppy_drive_emulator/index.html#stm32hxc
https://hxc2001.com/store/
@jedimatt42 : Conversion to HFE is not needed anymore with the hxc firmware.