How to silently prevent Webform spam (specific names, email addresses)? I am using Webform on Drupal 8; I have a few spambots that fill out the exact same form in the same way every day.

I want to do some kind of validation that automatically blocks these postings.  For example, if the name given is "Spambot 1", I want to discard the webform submission automatically.

Drupal 7 has the Webform Validation module but this has not yet been ported to Drupal 8.

I found a code snippet on adding custom validation to a webform element, but this seems to be for providing helpful errors to allow the user to re-submit the webform, whereas I want to make it seem like the form was submitted but silently discard the submission.
All the available SPAM protection modules for Drupal 8 are listed on the Webform Add-ons documentation page.

Text inputs now support patterns, you could explore creating a negative lookahead pattern like ^(?!.spam).$,