The Allwinner H2+ powered SBC runs Armbian's Debian and Ubuntu images and measures just 52 x 46 mm. The tiny board features 802.11 b/g/n Wi-Fi, Ethernet, up to 512 MB of RAM, USB 2.0 Type-A and a microSD card slot. There is a 26-pin unpopulated GPIO header too, along with a 13-pin header for headphone, USB 2.0, TV-out, microphone and IR signals. The Orange Pi Zero LTS currently costs between US$8.49 and US$10.49 depending on the version you buy and is available to order on AliExpress now.
https://www.notebookcheck.net/Orange-Pi-Zero-LTS-A-new-Raspberry-Pi-alternative-that-costs-US-10-and-should-run-cooler-than-its-predecessor.428908.0.html