🇷🇺Russia @pvasili

For Bootstrap 5.3.3 you need to roll back the npm sass module to version 1.77.6:

npm i sass@1.77.6 --save-exact

See details here

And/Or wait new for Bootstrap version :).

…
  $query1->union($query2, 'UNION ALL');
  $query1 = $query1->extend('PagerDefault');                  
  $results = $query1->execute();
…

we can try to do

…
  $query1->union($query2, 'UNION ALL');
  $query_pagination = db_select($query1,'q')->fields('q');
  $query_pagination = $query_pagination->extend('PagerDefault');
  $results = $query_pagination->execute();      
…