Github action which tags major version bumps from dependabot with 'major-version-bump' label. Note: You need to add the 'major-vesrion-bump' label to your repo manually.

tag-major-versions.yml

name: Tag Major Version Bumps

on:
  pull_request:
    types: [opened]
    branches:
      - main

jobs:
  tag-major-update:
    runs-on: ubuntu-latest
    if: github.actor == 'dependabot[bot]'
    steps:
      - name: Checkout code
        uses: actions/checkout@v2

      - name: Tag major version bump
        uses: actions/github-script@v7
        with:
          script: |
            const title = context.payload.pull_request.title;
            const versions = title.match(/Bump \S+ from (\d+)\.\d+\.\d+ to (\d+)\.\d+\.\d+/);
            if (versions && versions[1] !== versions[2]) {
              console.log(`Major version bump detected: ${versions[1]} -> ${versions[2]}`);
              await github.rest.issues.addLabels({
                owner: context.repo.owner,
                repo: context.repo.repo,
                issue_number: context.payload.number,
                labels: ['major-version-bump']
              });
            }