Most RP2040 boards these days are supported by the arduino-pico repository GitHub - earlephilhower/arduino-pico: Raspberry Pi Pico Arduino core, for all RP2040 boards.
The Pico4ML is not currently supported, as the repository owner doesn’t have this board.
Documentation for adding the Pico4ML can be found here https://github.com/earlephilhower/arduino-pico/blob/master/docs/contrib.rst
Please note the Pico4ML does work currently under the “generic” board type with Arduino IDE and this library, but by adding support you can include the TinyML and devices support.