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.

As a follow up to my original post, the author of the statically recompiled (SR) port of Septerra Core recently fixed the mouse lag/jitter that occurs with high polling gaming mice. All you need to do is edit the included Septerra.cfg and change CPU_SleepMode to reduced or nosleep.

I believe this to be the easiest way to get this game fully functioning with Windows 10, considering you just have to drag and drop the port into a vanilla Septerra Core GOG folder and run the new SR-Septerra.exe.

As an added bonus there exists more options such as v-sync, resolution changes and other quality of life fixes in the septerra.cfg

The links again:
https://github.com/M-HT/SR
https://github.com/M-HT/SR/releases (The direct link)

Thank you very much for your help and supporting the community :)

I've tried the SR port (currently v1.04.0.7) on Windows 11 and while it works like a charm, changing the display to fullscreen at 1080p causes the mouse icon to disappear from the main menu. I can circumvent the problem pretty easily by playing only in windowed mode but I'm not sure why it is giving me this issue.

...

How did you change to window mode? I have no figured out how to do that. I am using this:
https://www.zombs-lair.com/post/definitive-edition-patcher-septerra-core
since this is what i found first. It has some nice quality of life, but the one thing I am having trouble with is alt-tabbing. I was looking to stream this game, but I need to be able to alt-tab to do chat commands and such, and when I alt-tab, I can't tab or click back into the game.