Great replacement board, but there is one catch in flashing FW.
With Marlin v2.0 and above, the board becomes case sensitive. So once you upgrade the firmware to this version, the only way to flash again is to use all CAPS in the name of the new firmware. Instead of the default "firmware.bin", you need to rename it to "FIRMWARE.BIN" for the next upgrade to work. Be especially careful in a Windows environment with default hidden extensions. To rename in Windows, you must first rename it to something else and then rename it to uppercase letters (watch for the file extensions as they must be visible).
This is not a BTT bug, but something common to most 32-bit boards and new versions of Marlin.