Here's my solution using only Graph API Explorer & Access Token Debugger:
- Graph API Explorer:
- Select your App from the top right dropdown menu
- Select "Get User Access Token" from dropdown (right of access token field) and select needed permissions
- Copy user access token
- Access Token Debugger:
- Paste copied token and press "Debug"
- Press "Extend Access Token" and copy the generated long-lived user access token
- Graph API Explorer:
- Paste copied token into the "Access Token" field
- Make a GET request with "PAGE_ID?fields=access_token"
- Find the permanent page access token in the response (node "access_token")
- (Optional) Access Token Debugger:
- Paste the permanent token and press "Debug"
- "Expires" should be "Never"
(Tested with API Version 2.9-2.11, 3.0-3.1)