While shopping for TMC2209 stepper drivers I found advertisements "SD2209". Is this the same thing?
From what I can tell, the SD2209 is not a clone of or another name for the TMC2209, but is a board with a TMC2209 on it setup to be used as a drop-in replacement for other stepper drivers. See e.g. this SD2209 a drop-in replacement for Pololu style drivers: