This was deliberate to improve performance as the previous default encouraged users to do a performance intensive "contains" search on all fields. My suggestion would be to configure a search box on the dashboard to search the relevant fields that makes sense to search. You can choose up to 5 fields or select a report to use for the search.
Advanced search defaultsAdvanced search is available from Search on the global bar and on home pages of tables containing more than 10,000 records. We changed the default search option from <Some field> contains to Select a field. This encourages users to select a �contains� search only when necessary and may improve performance.
https://www.quickbase.com/quickbase-blog/april-2017-release-notes
