slices.SortFunc is coming soon:

https://pkg.go.dev/slices#SortFunc

but its not here yet. meanwhile, the signature:

func SortFunc[S ~[]E, E any](x S, cmp func(a, b E) int)

is different from x/exp/slices:

func SortFunc[E any](x []E, less func(a, b E) bool)

https://pkg.go.dev/golang.org/x/exp/slices#SortFunc

namely, the callback returns int instead of bool.