How to use Dompdf with Entity Print without composer?
I have been using the same module and was able to get it setup with Dompdf. Here are the steps in detail I used.

Summarized steps:


composer require drupal/entity_print (this automatically downloads the dompdf dependency for me)
On the content type, I enabled the custom display setting of PDF
Followed steps in "From your theme" to create the print.css and twig templates
composer require dompdf/dompdf (in case #1 doesn't download it)


Alternative: Ludwig module