Firebird RDBMS offers ANSI SQL features & runs on Linux, Windows & several Unix platforms. Features excellent concurrency & performance & powerful stored procedure & trigger language.
More information and downloads at https://firebirdsql.org/, issue tracker is https://github.com/FirebirdSQL/firebird/issues
SQL Embedded Manager, is a light-weight implementation of the SSMS.
The SQL Embedded Manager, is a Windows Forms light-weight implementation of the Microsoft SQL Server Management Studio, focused to supporting only all the embedded databases engines (for example, Sql Server Compact Edition, SQLite and Firebird).