renovate.json

{
  "$schema": "https://docs.renovatebot.com/renovate-schema.json",
  "extends": ["github>jkroepke/renovate-config:github-action"],
  "customDatasources": {
    "dotnet-sdk": {
      "defaultRegistryUrlTemplate": "https://dotnetcli.blob.core.windows.net/dotnet/release-metadata/releases-index.json",
      "transformTemplates": [
        "{\"releases\": [$.\"releases-index\"[ $.\"support-phase\" = \"active\" ].{\"version\": $.\"latest-sdk\"}]}"
      ]
    }
  },
 "customManagers": [
    {
      "customType": "regex",
      "managerFilePatterns": [
        "/README.md/"
      ],
      "matchStrings": [
        "\\*\\*\\.NET SDK (?<currentValue>\\S+)\\*\\*"
      ],
      "datasourceTemplate": "custom.dotnet-sdk",
      "depNameTemplate": "dotnet-sdk"
    }
  ]
}