The success continues: A new bios update became available for my MSI motherboard this week, and I used my newly working install to write it to the flash chip thus:

root@clay-MS-7C37:~# flashrom -p internal -w E7C37AMS.HB0 -V

And it worked! I now have successfully updated my bios with flashrom.

On Thu, Nov 5, 2020 at 12:58 AM Clay Daniels <clay.daniels.jr@gmail.com> wrote:

All the pieces finally came together. I made a fresh install of Ubuntu, installed all the needed tools. cloned flashrom, modified sb600spi.c per Rene's patch to include my AMD X570 "0x61" spi, did a make install, and it works!

root@clay-MS-7C37:~# flashrom -p internal
flashrom v1.2-135-g07edbb9-dirty on Linux 5.8.0-26-generic (x86_64)
flashrom is free software, get the source code at https://flashrom.org
Using clock_gettime for delay loops (clk_id: 1, resolution: 1ns).
Found chipset "AMD FP4".
Enabling flash write... Warning: spireadmode not set, leaving spireadmode unchanged.Warning: spispeed not set, leaving spispeed unchanged.OK.
Found Winbond flash chip "W25Q256.W" (32768 kB, SPI) mapped at physical address 0x00000000fe000000.
No operations were specified.
root@clay-MS-7C37:~#

Thanks to everyone,
Clay
(Boot_Dawg)