The search engine calculates a score that aggressively favors text-heavy websites, and punishes those that have too many modern web design features.
This is in a sense the opposite of what most major search engines do, they favor modern websites over old-looking ones. Most links you find here will be nearly impossible to find on a regular search engine, as they aren't sufficiently search engine optimized.

Vendor blurb:

OpenSearch is a community-driven, open source search and analytics suite derived from Apache 2.0 licensed Elasticsearch 7.10.2 & Kibana 7.10.2. It consists of a search engine daemon, OpenSearch, and a visualization and user interface, OpenSearch Dashboards. OpenSearch enables people to easily ingest, secure, search, aggregate, view, and analyze data.