Swonk prefers Orange Pi single board computers. They're cheap and available in a range of sizes / feature sets.
The basic Orange Pi hardware is pretty good, although the Wifi isn't well supported. Software support is the big problem. The operating system images provided by the manufacturer, Xunlong, are not very good. The boards are supported by OpenBSD, and Armbian Linux. There is also H3droid, a nice Android implementation.
The Raspberry Pi is the mainstream SBC. If you want good support, software that just works, this is the goto option. Cost and performance are not always the greatest, but it is good, reliable, and well understood. The Raspberry Pi community is best feature of the Raspberry Pi.
The Beagle Board family of single board computers has been around almost as long as the Raspberry Pi.
All these SBCs had the option to use a serial console.