So for those unaware, there exists a statically recompiled (SR) port of Septerra Core which still seems pretty active (last updated Apr 13 as of this message). It can also play the GOG install movies and has so far worked flawlessly for me (once set up properly) in my current run on Windows 10 (winver 1909)

Installation is as easy as downloading https://github.com/M-HT/SR/releases and drag 'n dropping the files into your original install directory. Can also rename/delete the ddraw.dll if you desire (I did). Make sure to run the game using the new SR-Septerra.exe

Editing Septerra.cfg will grant you access to VSYNC and fullscreen.

So the interesting note. If your mouse polling is set too high then the mouse movement will be jerky, much like the current GOG install. Set it lower though, and the movement is once again buttery smooth. For example, with my Logitech G603 I can turn it over to endurance mode using a physical switch. Other gaming mice may be able to change it using their own specific software.

You can use this website https://zowie.benq.com/ja/support/mouse-rate-checker.html to check your current mouse polling rate. When I switch from High Performance to Endurance I go from an average 1000 Hz to 125 Hz. So I would make 125 Hz the target goal for playing the Septerra Core SR port smoothly.