A script to set the author byline of a modern SharePoint page using PnP PowerShell

Set-PageHeader-Author-Byline.ps1

Param(
    [Parameter(mandatory = $true)]
    [string]$SiteUrl,
    [Parameter(mandatory = $true)]
    [string]$PageName,
    [Parameter(mandatory = $true)]
    [string]$UserEmail
)

function Set-PageHeaderAuthor {

    # Connect to the site
    Connect-PnPOnline -Url $SiteUrl;

    # If there is an error in the connection then return
    if ($null -eq $(Get-PnPConnection).ConnectionType) {
        return;
    }

    # Get the page object from the specified page name / url 
    $page = Get-PnPPage -Identity $PageName;

    # Return if page is not found
    if ($null -eq $page) {
        Write-Error "Page Name is not valid";
        return;
    }

    # Get the required user from the User Information list
    Write-Host "Getting user information from User Information list..." -ForegroundColor Yellow;
    $user = Get-PnPUser | Where-Object Email -eq $UserEmail;

    if ($null -ne $user) {
        Write-Host "Got user information from User Information list." -ForegroundColor Yellow;
    }
    else {
        # If not user is not present in User Information list then add the user to the list
        # This will not affect any permissions to the site
        Write-Host "User information not present in User Information list, hence adding..." -ForegroundColor Yellow;
        $user = New-PnPUser -LoginName $UserEmail; 

        # Return if the user is not found / email address is incorrect
        if ($null -eq $user) {
            Write-Error "User Name is not valid";
            return;
        }
    }

    Write-Host "Setting page header author..." -ForegroundColor Yellow;

    # Set the Authors and AuthorByLine properties of the PageHeader
    # Both these are string properties
    $page.PageHeader.Authors = "[{`"id`":`"$($user.LoginName)`"}]";
    $page.PageHeader.AuthorByLine = "[`"$($user.Email)`"]";

    # Save the chnages and publish the page
    $page.Save() | Out-Null;
    $page.Publish();

    Write-Host "Done." -ForegroundColor Green;
    Disconnect-PnPOnline;
}

Set-PageHeaderAuthor;

# Set-PageHeader-Author-Byline.ps1 -SiteUrl https://tenantname.sharepoint.com/sites/sitename -PageName Page-1.aspx -UserEmail user@tenantname.onmicrosoft.com