If you’re looking for a good platform for using uLisp with SD cards I can recommend Adafruit’s new Feather RP2040 Adalogger board:
Built to the same high standard as Adafruit’s other Feather-format boards, it includes 8 Mbytes of flash, a microSD socket, a NeoPixel RGB LED, a Stemma QT connector giving access to the I2C port, and a LiPo battery connector with charging via the USB C port. For more details see:
Adafruit RP2040 Feather boards
The 4.6a release of ARM uLisp adds support for the board, and includes a new directory command to list the files on an SD card; see: