Due to historical reasons, FYSETC provides two versions of bootloaders that can be downloaded here:

Older motherboards shipped prior to June 23 2021 use a 64k bootloader: Bootloader_FYSETC_SPIDER_10000.hex

Current motherboards shipped after June 23 2021 use a 32k bootloader: Bootloader_FYSETC_SPIDER.hex

Go to the FYSETC github. You need to download the bootloader. Right click on the file and select "save link as..." and save the .hex file

Open the .hex file in Notepad++ and you see it downloads the html data instead of the .hex file.

On the Github page click on Bootloader_FYSETC_SPIDER.hex

Select "Raw". Copy the data in the web browser and paste it into the .hex file in Notepad++ and save it.