System tampering detector for USB, Bluetooth, AC, Battery, Disk Tray, and Ethernet. Ostensibly shuts the whole thing down but can be configured to do other stuff. I don't know how reliable it is, haven't audited the code yet. Written in Python.
TERES-I Do-It-Yourself Free Open Source Hardware and Software laptop with ARM64 and x86 processors. Comes as a kit or a bunch of spare parts. FOSH/FOSS. ARM64, x86, MIPS variants. Can be upgraded piecemeal. Definitely runs Ubuntu and Android, can probably run other ported distros with a bit of work. Has all of the features and components that you'd expect, from wireless to a built-in webcam. Of course, you can probably leave out the stuff you don't want.
The Novena is a completely open source laptop (free and libre') based around the 64-bit quad-core Cortex A9 CPU and Vivante GC2000 GPU. Every single aspect of the project is NDA-free - no licensing fees, no restrictions on what you can do with it or say about it. Full accessible documentation. Tops out at 4GB of RAM.