ITS has posted a hotfix for the most recent beta release of UT Drupal Kit 3.0 (UTDK 3).
The 3.0.0-beta.8.1 release resolves a bug introduced in the 3.0.0-beta.8 release, which was made publicly available on November 10, 2020.
Specifically, the bug would cause an unrecoverable white screen on pages that contained Promo Units that were configured to use any display other than the default.
This is resolved in 3.0.0-beta.8.1. Sites that already updated to 3.0.0-beta.8 should update to 3.0.0-beta.8.1 to fix this issue.