We are aware of changes resulting in search not returning results as expected when “Include in dashboard” is disabled for the library. The option was always meant to also remove things from search because we thought that if you did not want it on your dashboard you probably would not want it to show up in search unless specifically browsing that library. (For example, not showing search results for an adult library on the family TV.)
Taking into account user feedback about the change, we will be bring back the feature as it behaved before but also adding another option for those that choose to use it. The new option allows you to exclude the library contents from search results. This change should be available in an upcoming beta and then public after that.