@ric96 IIRC dragonboard410c_sdcard_developer_debian-252.zip is used for booting from SD card itself (i.e., without flashing onto eMMC)
dragonboard410c_sdcard_install_debian-252.zip is used to flash eMMC using image in SD card.
In your case you might want to use the first one. If you want to create a bootable SD card on your own, you can refer the below link:
Hope this helps!