Here it says GPL-3.0-or-later:
GPL-3.0-or-later
https://gitlab.freedesktop.org/hadess/switcheroo-control/-/blob/cf450abea511e767ea0123157fb7e59e7b5eaf08/meson.build#L3
Here GPL-3.0-only:
GPL-3.0-only
https://gitlab.freedesktop.org/hadess/switcheroo-control/-/blob/cf450abea511e767ea0123157fb7e59e7b5eaf08/src/switcheroo-control.c#L4-6