There is a plug-in called System Dark Mode, but as discussed here it’s not working on Android.
I hope it will be modified to allow times to be specified, until the system-based switch can be implemented.
Or someone who knows more coding than me could adapt the code and release a version with time-based settings?
EDIT:
“This topic was automatically closed 24 hours after the last reply” and my answer was the “accepted solution”?
Wut? No, still broken! Maybe someone could kindly tag me if an actual solution is found.