Librem 5 EXT CON Rigid-Flex Breakout Board
Purism
The EXT CON Rigid-Flex Breakout Board is a small board that connects to the FPC connector J10 on the Librem 5 while the rigid section mounts inside of the phone using the center M.2 cover-plate threaded insert. The breakout board provides UART, I2C, SPI, two GPIOs, 3.3V, and 1.8V; making it really useful for custom projects, as demonstrated in this blog post.