jq ' from_entries'

cat data/ann.json | jq '.metadata.annotations | to_entries | map(if .key | contains("label") then .value="kuku" else . end) ' cat data/ann.json | jq '.metadata.annotations | to_entries | map(if .key | contains("label") then .value="kuku" else . end) | from_entries' 
[
  {
    "key": "deployment.kubernetes.io/revision",
    "value": "1"
  },
  {
    "key": "machine.openshift.io/owned",
    "value": ""
  },
  {
    "key": "label1",
    "value": "kuku"
  },
  {
    "key": "label2",
    "value": "kuku"
  },
  {
    "key": "label3",
    "value": "kuku"
  }
]
    
{
  "deployment.kubernetes.io/revision": "1",
  "machine.openshift.io/owned": "",
  "label1": "kuku",
  "label2": "kuku",
  "label3": "kuku"
}