The ConvertFrom-iTerm2.ps1 script takes an iTerm2 color scheme and outputs JSON you can put into a Windows Terminal color scheme. You either specify an http(s) URL to an itermcolors file which it will download and output JSON, or pass it an already downloaded file. In case of the former use the -ColorFileURL switch, in case of the latter use the -ColorFile switch.
You can find iTerm2 color schemes here for instance.
Example:
The above pulls the Ubuntu colour theme, which I can input into Windows Terminal to get something like this:
See this blog post for the background on this.
Tested with PowerShell 7/ PowerShell Core so it works on Linux & macOS.