I've been looking into doing an SBC K8s cluster, but had my eyes on the ODroid N2+. Its big.LITTLE design with 4 high-performance cores and 2 low-performance ones would not only boost the compute capacity vs the RPi4, but also perhaps cgroups on the nodes could be configured such that pods only run on the 4 high-performance cores, leaving the 2 low-performance ones available for system daemons, kubelet, etc. The biggest drawback with the N2 is that it maxes out at 4GB of RAM, which might not be sufficient for the cluster master nodes. So maybe the master nodes could be 8GB RPi4s, while all the worker nodes are N2s.