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    Bug 
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    Resolution: Fixed
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    P3: Somewhat important 
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    6.7
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    None
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        434494dfb (dev), 9844da503 (dev), f18862e91 (6.8)
https://bugreports.qt.io/browse/QTBUG-111879 added support for the Firebird 4 TIMESTAMP WITH TIME ZONE type. During first connect it populates a timezone cache, if you compiled it with the Firebird 4 library.
However, if you connect to a pre-v4 Firebird database, this fails because the necessary table does not exist. It needs a runtime rather than compile time check for Firebird 4.