$ juju status
Model       Controller  Cloud/Region        Version         SLA          Timestamp  Notes
controller  upgrade     microk8s/localhost  2.8-beta1.3572  unsupported  17:58:56Z  upgraded on "2020-04-23T17:56:51Z"

App              Version  Status   Scale  Charm            Store       Rev  OS          Address         Notes
mariadb-k8s               active       1  mariadb-k8s      jujucharms    2  kubernetes  10.152.183.11
ubuntu                    waiting    0/1  ubuntu-plus-k8s  local         1  kubernetes                  agent initializing
ubuntu-plus-k8s           active       1  ubuntu-plus-k8s  local         0  kubernetes  10.152.183.106


Unit               Workload  Agent       Address     Ports     Message
mariadb-k8s/0      active    idle        10.1.59.38  3306/TCP
ubuntu-plus-k8s/0  waiting   idle        10.1.59.36  3306/TCP  Hello from start, it is 23/04/2020 17:54:48
ubuntu/0           waiting   allocating                        agent initializing

$ microk8s.kubectl get all --all-namespaces
NAMESPACE            NAME                                        READY   STATUS    RESTARTS   AGE
controller-upgrade   pod/controller-0                            2/2     Running   0          10m
controller-upgrade   pod/mariadb-k8s-0                           1/1     Running   0          12m
controller-upgrade   pod/mariadb-k8s-operator-0                  1/1     Running   0          10m
controller-upgrade   pod/ubuntu-plus-k8s-779d566b87-9mxwh        1/1     Running   0          12m
controller-upgrade   pod/ubuntu-plus-k8s-operator-0              1/1     Running   0          10m
kube-system          pod/coredns-588fd544bf-2jtwx                1/1     Running   0          100m
kube-system          pod/hostpath-provisioner-75fdc8fccd-d8gxl   1/1     Running   0          100m

NAMESPACE            NAME                               TYPE        CLUSTER-IP       EXTERNAL-IP   PORT(S)                  AGE
controller-upgrade   service/controller-service         ClusterIP   10.152.183.67    <none>        17070/TCP                19m
controller-upgrade   service/mariadb-k8s                ClusterIP   10.152.183.11    <none>        3306/TCP                 12m
controller-upgrade   service/mariadb-k8s-endpoints      ClusterIP   None             <none>        <none>                   12m
controller-upgrade   service/mariadb-k8s-operator       ClusterIP   10.152.183.181   <none>        30666/TCP                12m
controller-upgrade   service/ubuntu-plus-k8s            ClusterIP   10.152.183.106   <none>        3306/TCP                 12m
controller-upgrade   service/ubuntu-plus-k8s-operator   ClusterIP   10.152.183.207   <none>        30666/TCP                13m
default              service/kubernetes                 ClusterIP   10.152.183.1     <none>        443/TCP                  102m
kube-system          service/kube-dns                   ClusterIP   10.152.183.10    <none>        53/UDP,53/TCP,9153/TCP   100m

NAMESPACE            NAME                                   READY   UP-TO-DATE   AVAILABLE   AGE
controller-upgrade   deployment.apps/ubuntu-plus-k8s        1/1     1            1           12m
kube-system          deployment.apps/coredns                1/1     1            1           100m
kube-system          deployment.apps/hostpath-provisioner   1/1     1            1           100m

NAMESPACE            NAME                                              DESIRED   CURRENT   READY   AGE
controller-upgrade   replicaset.apps/ubuntu-plus-k8s-779d566b87        1         1         1       12m
kube-system          replicaset.apps/coredns-588fd544bf                1         1         1       100m
kube-system          replicaset.apps/hostpath-provisioner-75fdc8fccd   1         1         1       100m

NAMESPACE            NAME                                        READY   AGE
controller-upgrade   statefulset.apps/controller                 1/1     19m
controller-upgrade   statefulset.apps/mariadb-k8s                1/1     12m
controller-upgrade   statefulset.apps/mariadb-k8s-operator       1/1     12m
controller-upgrade   statefulset.apps/ubuntu-plus-k8s-operator   1/1     13m

Steps:
/snap/bin/juju version = 2.7.6-focal-amd64
/snap/bin/juju bootstrap microk8s upgrade
/snap/bin/juju create-storage-pool mariadb-pv kubernetes storage-class=microk8s-hostpath
/snap/bin/juju create-storage-pool operator-storage kubernetes storage-class=microk8s-hostpath
/snap/bin/juju deploy ~/notes/charms/builds/ubuntu-plus-k8s --resource ubuntu_image=ubuntu
/snap/bin/juju deploy cs:~juju/mariadb-k8s --storage database=mariadb-pv,10M
juju upgrade-controller --agent-stream=develop
juju deploy ~/notes/charms/builds/ubuntu-plus-k8s --resource ubuntu_image=ubuntu ubuntu