libmono-system-data-linq4.0-cil 5.18.0.240+dfsg-5build1 (amd64 binary) in ubuntu focal

 Mono is a platform for running and developing applications based on the
 ECMA/ISO Standards. Mono is an open source effort led by Xamarin.
 Mono provides a complete CLR (Common Language Runtime) including compiler and
 runtime, which can produce and execute CIL (Common Intermediate Language)
 bytecode (aka assemblies), and a class library.
 .
 This package contains the Mono System.Data.Linq library which implements
 LINQ to SQL. LINQ to SQL allows one to query relational databases using the
 language-integrated query (LINQ) extension of the C# programming language.