For 22 of the following 23 instances (available in MiniZinc format and Essence format), the computed lower bound (lb) on $\lambda$ has been shown to be feasible.

$v$ $b$ $r$ lb($\lambda$)
9 300 100 25
10 325 100 24
10 350 100 22
10 360 120 32
15 350 100 24
19 20 9 4
9 70 35 16
10 100 30 7
11 150 50 14
12 200 75 25
13 250 80 22
6 50 25 10
6 60 30 12
8 28 14 6
9 36 12 3
10 30 9 2
11 22 10 4
12 44 11 2
13 26 6 1
15 21 7 2$^*$
16 16 6 2
19 19 9 4
10 37 14 5

$^*$ For the instance $\langle 15,21,7 \rangle$, the best known solution has $\lambda = 3$ and it is unkown whether there exists a solution that matches the computed lower bound of 2 (note that not much effort has been put into answering this question).