Original board Matrix Portal M4 has a space between "Matrix" and "Portal": https://circuitpython.org/board/matrixportal_m4/
New board MatrixPortal S3 mushes them together with no space: https://circuitpython.org/board/adafruit_matrixportal_s3/
The search on the downloads page turns up both boards if you search "matrixportal":

... but only turns up the M4 board if you search "matrix portal"!
