It is cheap, but it looks like you need to add a power supply, and for darkroom use you would want an enclosure. It would be easy to spend as much or more than the cost of a ready to use timer.
That said, if you have a bit of a DIY inclination, it's hard to beat the price.
It is functioning as a proper darkroom timer. It turn on and off the enlarger automatically.
Yes, you need a power supply, a box and 2 or 3 buttons. But you will get a proper digital darkroom timer.
Now I use an old, analog timer, which was cheap, but I can barely read the numbers in the dark and i think it is not so precise.
I live in Hungary, and there are no digital darkroom timers on the second hand market. Especially not for low cost.I believe it could be a good diy timer.