ZX Next Clones
The core of the Spectrum Next hardware is licensed under the GPLv3 free software license which has enabled the production of several compatible (and partly compatible) clones or ports, including:
N-Go - The N-Go is a full ZX Next clone complete with 2 Mega Drive style joystick ports, an expansion port and optional custom case.
Xberry Pi - an affordable Next clone with a PCB roughly the same dimensions as a Raspbery Pi 3.
ZX-DOS - FPGA-based hardware recreation of the ZX Spectrum, created by Antonio Villena.
ZX-DOS+ and gomaDOS+ - ZXDOS+ and gomaDOS+ are the continuation of ZX-Uno. They are the same machine in a different case.
ZXN core for MiSTer - A port of the Spectrum Next core to the MiSTer platform.
ZXTRES - The ZXTRES, ZXTRES+ and ZXTRES++ are Next clones with several alternative cores.ZXTRES wiki.
ZX-UNO - A Next clone in a Raspberry Pi form factor with composite video output.