I made progress and got the saber update to 5.9. I also enabled WebUSB now and I can see the SD card when the saber is plugged into my PC.
However, to do it, I had to manually update the driver to MSFT’s newest WebUSB driver.
First, I connected my saber and entered Arduino. Opened the Serial Monitor. Issued the RebootDFU command. Opened Device Manager for Windows and verified that STM32 BOOTLOADER was displayed there under “Other Devices”. Right clicked on that device and selected Update Driver.
And then, I followed Steps 1-7 at the following URL.
WinUSB (Winusb.sys) Installation - Windows drivers | Microsoft Docs
I am still troubleshooting my config. For instance, I am now seeing errors when I issue the effects command in the serial monitor. It shows something about unnumbered files in one of my fonts or folders… Not sure yet.