Text to go in the release notes:
This changes the behavour of title search and sorting (Title (A-Z)) in the OPAC and staff interface when using Elasticsearch or Open Search. The title search now only uses 245 (for MARC 21) and 200 (for UNIMARC). Previously other title fields may have affected the search order, for example 240$a in MARC21.
To make this change for existing installations, reset the search engine mappings (Administration > Catalog > Search engine configuration (Elasticsearch) > Reset mappings (scroll down to the bottom of the page)) and rebuild the search index (koha-elasticsearch --rebuild -d -b -a <instancename>). If you have customized the search engine configuration, remember to record or back these up BEFORE resetting the mappings.