same error.
Brand new user (just received my M5StickC 7 hours ago)
My development environment is freshly minted (3 hours ago) on a USB drive plugged into a Raspberry Pi4B.
New OS. New install of Arduino IDE 1.8.19.
Add platform "M5Stack Arduino" and Library "M5StackCPlus" by following these instructions.

the sketch is very basic
'''
void setup() { }

void loop() { }
'''

the error is:
usage: esptool write_flash [-h] [--erase-all]
[--flash_freq {keep,40m,26m,20m,80m}]
[--flash_mode {keep,qio,qout,dio,dout}]
[--flash_size FLASH_SIZE]
[--spi-connection SPI_CONNECTION] [--no-progress]
[--verify] [--encrypt]
[--encrypt-files <address> <filename> [<address> <filename> ...]]
[--ignore-flash-encryption-efuse-setting]
[--compress | --no-compress]
<address> <filename> [<address> <filename> ...]
esptool write_flash: error: argument <address> <filename>: Address "{upload.erase_cmd}" must be a number
esptool write_flash: error: argument <address> <filename>: Address "{upload.erase_cmd}" must be a number

Please assist with getting my shiny new device to work.

Dear M5: please repair the board information for the M5Stick-C-plus. See errors above.

other users: switching to the M5Stick-C (no "-plus") platform allowed me to upload new sketches to the device.

Dear M5: please repair the board information for the M5Stick-C-plus. See errors above.

other users: switching to the M5Stick-C (no "-plus") platform allowed me to upload new sketches to the device.

the file does actually show the "-e". What should it be?
~/.arduino15/packages/m5stack/hardware/esp32/2.0.5/boards.txt

m5stick-c.menu.EraseFlash.none=Disabled
m5stick-c.menu.EraseFlash.none.upload.erase_cmd=
m5stick-c.menu.EraseFlash.all=Enabled
m5stick-c.menu.EraseFlash.all.upload.erase_cmd=-e

Any idea if the "Factory Test" included in M5Burner is the same as the "FactoryTest" in the Arduino library example?

I see this referenced in many threads here on the forum, but I do not see anything definitive.
Also there are no comment in the code that could clarify this...

Is the example sketch "FactoryTest" the code that ships preloaded on a new device (mine is M5StickC-plus) ?

(it'd be nice as a safety-net to fall back to should I mess up something while learning)

same error.
Brand new user (just received my M5StickC 7 hours ago)
My development environment is freshly minted (3 hours ago) on a USB drive plugged into a Raspberry Pi4B.
New OS. New install of Arduino IDE 1.8.19.
Add platform "M5Stack Arduino" and Library "M5StackCPlus" by following these instructions.

the sketch is very basic
'''
void setup() { }

void loop() { }
'''

the error is:
usage: esptool write_flash [-h] [--erase-all]
[--flash_freq {keep,40m,26m,20m,80m}]
[--flash_mode {keep,qio,qout,dio,dout}]
[--flash_size FLASH_SIZE]
[--spi-connection SPI_CONNECTION] [--no-progress]
[--verify] [--encrypt]
[--encrypt-files <address> <filename> [<address> <filename> ...]]
[--ignore-flash-encryption-efuse-setting]
[--compress | --no-compress]
<address> <filename> [<address> <filename> ...]
esptool write_flash: error: argument <address> <filename>: Address "{upload.erase_cmd}" must be a number
esptool write_flash: error: argument <address> <filename>: Address "{upload.erase_cmd}" must be a number

Please assist with getting my shiny new device to work.