Hi,
You're right. Check this document link https://cdrdv2-public.intel.com/666495/ug-683865-666495.pdf (page 6):
You need to program the configuration data into the configuration flash memory (CFM) before internal configuration can take place. The configuration data to be written to CFM will be part of the programmer object file (.pof). Using JTAG In-System Programming (ISP), you can program the .pof into the internal flash.During internal configuration, Intel MAX 10 devices load the CRAM with configuration data from the CFM.
I think only through JTAG is possible.
Thanks,
Best Regards,
Sheng