Canonically in Voyager their computers run macOS. BSD is pretty great.
There a scene with a macOS cursor visible.
Mach/BSD 🤓
The actual kernel of XNU (ie. what's under the hood in macOS, originally by NeXT) is Mach which is a microkernel, and a chunk of FreeBSD is used to provide userland(ish) stuff like POSIX APIs, a UNIX process model on top of Mach, protocol stacks 'n shit.
but this means they are PowerPC Macs...
Just eject the warp core ... and reinsert it again.
Like a battery when you want to restart your device.
LCARS already has a UNIX kernel. Didn't you know that?
There is an LCARS desktop environment for Linux https://lcarsde.github.io/
I did not!
I didn't either, but it sounded plausible.