Dark mode will be in the next release, 15.1, which is due out in mid-late January.
If you upgrade to 15.0 now, then you can also install the beta and try it out in beta.
Dark mode will be in the next release, 15.1, which is due out in mid-late January.
If you upgrade to 15.0 now, then you can also install the beta and try it out in beta.