Firebird has now been integrated into LibreOffice master!
It now builds on Mac and Windows in addition to Linux. (I’ve only tested on Linux but will be testing/fixing as necessary on Mac/Windows this week.)
The database driver itself is almost unusable at the moment as I’ve been refactoring various things to do with transaction control and execution of statements. More and more functionality should be appearing in the course of this week, making the driver more usable .
For now hsqldb will still be the default embedded db. To use firebird for embedded files you either have to set EmbeddedDatabases/DefaultEmbeddedDatabase/Value in the registry to “sdbc:embedded:firebird”; or create a new .odb file with base, edit the content.xml within and replace “sdbc:embedded:hsqldb” with “sdbc:embedded:firebird”, then reopen the .odb. At the moment the driver can only work with databases embedded in the .odb; support for external and/or remote databases however doesn’t look particularly complicated so should hopefully appear soon.