The game doesn't require D3D12 as far as I can tell. I'm using Wine on Linux, but the game starts with D3D11, even if Wine is set to behave like Windows 10. (Granted, I had to do my own fiddling for it to work, but that's not really relevant...) Regardless, you can force either one with `-force-d3d11` or `-force-d3d12` on the command line.
Also, Windows programs do like to choke on so-called "invalid characters", but having a colon in a file path is not going to corrupt your disk or otherwise cause you to lose data. If NTFS didn't support arbitrary file names, it wouldn't have let you extract the zip at all (you can use filenames with colons in NTFS on Linux and it works just fine!). It will still make things obnoxious on Windows, but that's unfortunately the name of the game with it...
Anyway, supporting older rendering backends is all well and good, but frankly there's nothing wrong with using Unity. It's just another tool that a developer can choose to use if they feel comfortable with it; it doesn't make the game less valid, even if it seems extreme to you. It is unfortunate that it seemingly no longer supports anything <D3D11, and supporting OpenGL or Vulkan on Windows requires explicit action from the developer... Fortunately, though, these days DXVK (the D3D-to-Vulkan translation layer normally used to run Windows games on Linux) can be used on Windows for GPUs with Vulkan support, which can come in handy in some cases :)
