Hi Grant.
I’ve been using Firebird with Delphi for more than 18 years now - accross many demographics (Home, Corporate and Government).
For Delphi and FPC interface I use ZeosLib (ZeosLib download | SourceForge.net). Opensource.
For Database Management I use Database Workbench (Database Workbench: database development tool for MySQL, MariaDB, Oracle, Firebird, PostgreSQL, Postgres, InterBase, SQL Anywhere, Microsoft SQL Server and NexusDB @ Upscene Productions). But - depending on your requirements - may be more than you need).
If you want to get to know Firebird in depth, Helen Borrie’s “The Firebird Book” is really excellent (just make sure it’s the most recent adiotion).
And - for general Firebird stuff -
https://www.firebirdnews.org/
and
http://www.firebirdsql.org/