Searching from the backoffice as well as from the code (if Umbraco is runnig from Visual Studio) crashes with the following error:

Method not found: 'Void Lucene.Net.Search.Query.ExtractTerms(System.Collections.Generic.ISet`1<Lucene.Net.Index.Term>)'.

Exception Details
System.MissingMethodException: Method not found: 'Void Lucene.Net.Search.Query.ExtractTerms(System.Collections.Generic.ISet`1<Lucene.Net.Index.Term>)'.
Stacktrace
   at Examine.LuceneEngine.LuceneSearchResults.DoSearch(Query query, IEnumerable`1 sortField, Int32 maxResults)
   at Examine.LuceneEngine.Search.LuceneSearchQuery.Search(Int32 maxResults) in C:\projects\examine-qvx04\src\Examine\LuceneEngine\Search\LuceneSearchQuery.cs:line 159
   at Examine.LuceneEngine.Search.LuceneBooleanOperation.Execute(Int32 maxResults) in C:\projects\examine-qvx04\src\Examine\LuceneEngine\Search\LuceneBooleanOperation.cs:line 46

Absolutely incomprehensibly the same published (from Visual Studio) on hosting works. Last update of everything.

It was probably my mistake in referring to Lucene. Currently, this does not end at error, but the searching does not work (no results). Correct referencing Examine and Umbraco.Examine helped. However, the index is apparently not created. I found that in version 7, its creation started by default at startup. What probably doesn't work.