I'm trying to build a docker image for a self-contained dotnet app to run on linux from a Windows build (using the Visual Studio 2017 image) which is required to build and deploy a local SQL Server instance that is used to build and test the app. The build fails to create the docker image with the following comment, which I understand to mean that it's trying to build a Windows image, not a Linux image:

no matching manifest for windows/amd64 in the manifest list entries

I've seen several threads asking a similar question, which seems to be answered here: https://help.appveyor.com/discussions/questions/33953-docker-linux-.... However, I tried both updating to Visual Studio 2019 and copying the script suggested at the bottom of that thread, but I get failed builds with output like the following:

Get-LocalUser : User DockerExchange was not found.
At C:\projects\***\docker-appveyor.psm1:7 char:5
+     Get-LocalUser -Name $deUsername | Set-LocalUser -Password $secDeP ...
+     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : ObjectNotFound: (DockerExchange:String) [Get-LocalUser], UserNotFoundException
    + FullyQualifiedErrorId : UserNotFound,Microsoft.PowerShell.Commands.GetLocalUserCommand
 
& : The term 'C:\Program Files\Docker\Docker\DockerCli.exe' is not recognized as the name of a cmdlet, function, script file, or operable program. Check the spelling of the name, or if a path was included, verify that the path 
is correct and try again.
At C:\projects\***\docker-appveyor.psm1:8 char:7
+     & $env:ProgramFiles\Docker\Docker\DockerCli.exe -Start --testftw! ...
+       ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : ObjectNotFound: (C:\Program File...r\DockerCli.exe:String) [], CommandNotFoundException
    + FullyQualifiedErrorId : CommandNotFoundException
 
& : The term 'C:\Program Files\Docker\Docker\DockerCli.exe' is not recognized as the name of a cmdlet, function, script file, or operable program. Check the spelling of the name, or if a path was included, verify that the path 
is correct and try again.
At C:\projects\***\docker-appveyor.psm1:9 char:7
+     & $env:ProgramFiles\Docker\Docker\DockerCli.exe -Mount=D -Usernam ...
+       ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : ObjectNotFound: (C:\Program File...r\DockerCli.exe:String) [], CommandNotFoundException
    + FullyQualifiedErrorId : CommandNotFoundException

Is there updated guidance on this?