You may face the below issue while setting up Horizon on your machine.
And to resolve this issue, it is must verify is .net core 3.1 and 2.1 are on your machine. Please use the below command to verify
dotnet --info (PowerShell as admin)
If not then please install from below
https://dotnet.microsoft.com/en-us/download/dotnet/2.1
https://dotnet.microsoft.com/en-us/download/dotnet/3.1
Once installed, run horizon instance again.
The above same issue you may also face with Sitecore Identity server and solution will be same.
