This might be an issue with opensearch.xml, which is a standard for how browsers recognise search engines.

See here:

github.com/hnhx/librex/…/opensearch.xml.example

I don’t know how you’re hosting it, but when I was hosting LibreX, I had to make an opensearch.xml with the correct domain and bind mount it to the correct location. I don’t exactly remember the details since I moved to Searxng.

Also, if you’re not aware, LibreX was forked to LibreY, which is the updated repo.