Use Meta Conversion API without Meta Pixel ID

I was able to solve this as follows:

1. Disable PYS and Meta Pixel cookies in functions.php:
   add_filter( 'pys_disable_all_cookie', '__return_true', 10, 2 );
add_filter( 'pys_disable_facebook_by_gdpr', '__return_true', 10, 2 );
2. Disable existing Meta Pixel code in Google Tag Manager
3. Create a new Custom HTML Tag with the following code:
   <script>
pys.Facebook.loadPixel();
</script>

   Under consent settings -> Additional Consent Checks -> Require additional consent for tag to fire -> ad_storage

Seems to work nicely so far 👍