Due to "anti-features" introduced unilaterally by some people from FDroid community, it is not possible to find Organic Maps using the search in FDroid client without tinkering with its settings first: https://gitlab.com/fdroid/fdroiddata/-/issues/3347

By default, it is possible to find apps with ads, with tracking, with non-free network services, dependencies and assets, apps without source code and with known vulnerabilities. But it is not possible to find Organic Maps, an open-source app without ads and tracking.
https://cdn.fosstodon.org/media_attachments/files/113/050/148/770/333/065/original/32eee72d57136c08.jpg