I've flashed a SFR1M44-U100K Gotek with the HxC firmware. I have the HxC "logo" on the display on boot. I've removed all jumpers, except for the one on the S0 connector, as adviced.
I've tried to connect the gotek into an atari st external drive. However, I made a mistake, I've connected a multi voltage charger and forgot to change the correct voltage to 5v and I've used 9v instead, for a short time

The usb key chip was burned, but the gotek seems undamaged. I still have the hxc logo, and it displays correctly according to the config file on the new usb key (000 for autoboot, 000, then 001, 002... for indexed mode.) If I only put 4 files on a new usb key, the index will stop at 003, as expected.
But I can't make it read floppies on my atari st, now using the internal connectors, it's like there is no floppy inside.
Maybe some components were burned during the overvoltage, but before giving up, I wanted to know if there is something else I need to check for the configuration. I've also tried this on 4-5 different usb keys (between 500 mb and 8 gb, in fat32 or fat16 format)