The 12.6-inch Reform modular laptop runs Debian Linux and comes with a programmable firmware. Hardware-wise, components like the NXP i.MX8MQ quad-core ARM Cortex-A53 processor, Vivante GC700 Lite GPU and 4GB of RAM do not exactly scream performance, but they get the job done, plus they can be replaced later via module upgrades.
https://www.notebookcheck.net/MNT-Reform-modular-laptop-now-available-through-crowdfunding-campaign.464400.0.html