DMD Extender as far as I know is still available, but I haven't built a kit in years. I stopped updating the guide thread I wrote since there was really nothing more to add. I would strongly recommend the PinballSP DMDMK66. These are very high quality displays comprised of two 64x64 RGB LED panels. ColorDMD does offer these as well, but they are considerably more expensive. Software is on the way to allow custom full color frame by frame, but for now you can set a 4 color palette. There is also PIN2DMD, but stay away at all costs. The individual that sells the hardware for PIN2DMD is dishonest, plus it's low quality and untested anyway.

I have actually had my hands on two DMDMK66 displays by PinballSP and have installed one for a friend. It's very well built and is a single unit, no kits or extra cables needed. No extra software needed. It's all designed by a single person on a single circuit board.

https://pinside.com/pinball/biz/directory/1103-pinballsp

I mean it's very nice, but it's not the only objective answer. I'm giving him what options are available, not just the most popular one.

Yeah you won't be left out in the cold for sure. There are more options now than ever.