Tested on Ubuntu 25.04, 
sudo apt install libusb-1.0-0-dev
git clone https://github.com/raspberrypi/pico-sdk
git clone https://github.com/raspberrypi/picotool
cd picotool
git checkout de8ae5ac334e1126993f72a5c67949712fd1e1a4
export PICO_SDK_PATH="$(pwd)/../pico-sdk"
mkdir build
cd build
cmake ..
cmake --build . -- -j"$(npro)" VERBOSE=1build/picotool so copy it somewhere in your PATH like:cp picotool ~/binsudo ~/bin/picotool load -f build/zephyr/zephyr.uf2No accessible RP2040 devices in BOOTSEL mode were foundpico_enable_stdio_usb(blink 1)make sure that your program initializes the USB code via a call to "stdio_init_all()".
Ciro Santilli