This module provides EBI Ontology Lookup Service API http://www.ebi.ac.uk/ols integration to Drupal. It allows users to fill text fields with Ontology term autocomplete.
Branch 8.x-1.x is compatible with Drupal 8 and 9 simultaneously. https://www.drupal.org/docs/updating-drupal/how-to-prepare-your-drupal-7-or-8-site-for-drupal-9/preparing-drupalorg