So, the last version I was able to acquire and have been able to run in DOS is Eternity Engine 3.31 (beta7) built in the year 2004. And it works. Unfortunately, it has some weird mouse control. I'm able to make 180° turn just by fast mouse-pull. I've tried to customize mouse sensitivity, but so far I haven't been able to talk sense into it.   There is not such an issue in newer version (the mouse works perfectly smooth), so I have to raise question if there has been some patch or workaround over the years for DOS version of Eternity engine. Or if there is some backport available.