List of free search stuff for developer👇🏽
If you're looking for all programming tools around search (not just free). Check this page List of search Programming Tools
Typesense is a fast, typo-tolerant search engine optimized for instant search-as-you-type experiences and each of use.
Open source, free self hosted
An open source, blazingly fast and hyper relevant search-engine that will improve your search experience
Algolia is a flexible Search & Discovery Hosted API for Developers
Free up to 10 units (1 Unit = 1,000 search requests and the capacitcy index up to 1,000 records)