No matter how you choose to get the files, make sure that Popper is include before the picker's main script file.
You can grab the compiled js and css from GitHub
You still need to get Popper yourself.
<!-- Popperjs -->
<script src="https://cdn.jsdelivr.net/npm/@popperjs/core@2.9.3/dist/umd/popper.min.js" integrity="sha384-eMNCOe7tC1doHpGoWe/6oMVemdAVTMs2xqW4mwXrXsW0L84Iytr2wi5v2QjrP/xp" crossorigin="anonymous"></script>
<!-- Tempus Dominus JavaScript -->
<script src="https://cdn.jsdelivr.net/gh/Eonasdan/tempus-dominus@v6-alpha14/dist/js/tempus-dominus.js" crossorigin="anonymous"></script>
<!-- Tempus Dominus Styles -->
<link href="https://cdn.jsdelivr.net/gh/Eonasdan/tempus-dominus@v6-alpha14/dist/css/tempus-dominus.css" rel="stylesheet" crossorigin="anonymous">
Nuget package are returning! Coming Soon.