BarbecueCowboy

Very similar, but usually dramatically cheaper... Look into the Lenovo Tiny line of PCs, you can get a used model with a surprising amount of power for a lot less than you'd see in a comparable NUC and in my experience, they're usually hardier machines.

The argument from Signal seems to be that they don't want to expend resources supporting it or potentially federating with them. They do seem to have past experience doing this with CyanogenMod, and it sounds like it went poorly.