I saw some amazing news on the ZX Spectrum Next Facebook page:
Victor Trucco has released the sources of to TK-Pie. This device allows you to add HDMI output to your ZX Spectrum using a Raspberry Pi Zero. Just like the solution that can be found in the upcoming ZX Spectrum Next. Surprisingly it’s not based on Linux. Instead the Raspberry Pi runs its own baremetal OS. It intercepts video data being written to the ZX Spectrum VRAM. Pretty neat.