Hi!
TLDR; Mass Storage on STLINK on NUCLEO-C071RB isn't enabled by default. You need to use STLinkUpgrade to change Type to STM32 Debug+Mass Storage+VCP
I've got a new NUCLEO-C071RB for test purpose, to evaluate that it's ready to be programmed in my build environment. I quickly wanted to test it in the Arduino IDE with stm32duino board files. For simplicity I choose the upload method Mass Storage. I sat up the typical udev rules manually and added my user to dialout group, and restarted Ubuntu. After this, I still struggled to program the NUCLEO-C071RB board with Arduino IDE using the Mass Storage upload method.
That's when I had the idea to bring out a previous board I have laying around, NUCLEO-F401RE. Quickly after, this one was confirmed to work. At this moment i realized that NOD_F401RE was visible as an external storage on Ubuntu, while NOD_C071RB was not. Which confirmed that Mass Storage wasn't working on the NUCLEO-C071RB.
Update: I tried to see if there was any firmware updates for the STLINK. To keep the story short, STLinkUpgrade 3.16.8 requires additional permissions in Linux (Ubuntu 24.04) that I didn't look into. Ended up upgrading the STLINK firmware through Windows. Now I can program the NUCLEO-C071RB on my Ubuntu 24.04 computer with Arduino IDE utilizing the Mass Storage upload method.
(*) I read somewhere someone recommended using stws-link007 (Standalone STLinkUpgrade??). Which I see includes .sh scripts to setup udev rules. Possible that this script ensures access for firmware update for the STLINK with STLinkUpgrade software included in STM32CubeProgrammer.
