Repository edit events can include default branch changes and are dropped during parsing because it's missing from the types. (https://docs.github.com/en/webhooks/webhook-events-and-payloads?actionType=edited#repository)
{
"action": "edited",
"changes": {"default_branch": {"from": "master"}},
"enterprise": {
"description": "...",
"id": 1,
"name": "Inc"
},
"organization": {
"id": 1,
"login": "Inc"
},
"repository": {
"id": 1,
"name": "repo",
"full_name": "Owner/repo",
"owner": {},
"default_branch": "main"
},
"sender": {
"id": 1,
"login": "user"
}
}