Linux version of X3: Reunion is unfortunately 32 bit (developers should really stop making games 32 bit already). It crashes on startup with such error message:

Running X3: Reunion
*** X3 version 2.5 (Aug 11 2015 10:28:21) ***
../src/X3/s_linux/init.cpp : XMenuInit : 254 : dStub
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error opening prim. Catalog: 1
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EXIT(0)!!!
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I suspect it's one of the 32 bit games affected by big XFS partitions and not being built with -D_FILE_OFFSET_BITS=64. I'll test the workaround and update this report.

Is anyone still maintaining this port or it's already left to rot without support like happened with Brutal Legend?

UPDATE: Bug confirmed. The game works well in small loop XFS partition. I'm adding the game to the list: https://www.gog.com/mix/linux_games_with_large_xfs_partition_bug

The game works well in a small partition in xfs loop. But more to describe how you made a small partition in xfs loop. You edited it with nolargeio option or done differently. Unable to write in detail how you did it, if you do not mind