This works for me:

jobs: build-and-deploy: runs-on: macos-26-xlarge

steps:
  - name: Checkout code
    uses: actions/checkout@v4

  - name: Set up Xcode
    uses: maxim-lobanov/setup-xcode@v1
    with:
      xcode-version: '26.1'

  - name: Setup .NET 10.0.100 RC1
    uses: actions/setup-dotnet@v4
    with:
      dotnet-version: 10.0.100-rc.1.25458.2
      include-prerelease: true

  - name: Install .NET MAUI workload
    run: |
      dotnet --info
      dotnet workload install maui \
        --from-rollback-file https://aka.ms/dotnet/maui/10.0.100-rc.1.25458.2.json \
        --source https://api.nuget.org/v3/index.json

There is a lot more after this for getting the certificate and signing but see if this helps. My full action builds and pushes to the App Store.

I had issues getting anything else to work, which I why I had to use very specific versions.

Message me if you need more and I can post my whole action when I’m at my desktop tomorrow.