Can't get a Mac application bundle working

As the title says: I can’t get it working ever since upgrading from MG 3.6. I’m sure I’m doing something wrong, but for the life of me I can’t work out what it is and have been plugging away at it for too long, so I’m hoping to get a second set of eyes on the problem.

This is what the player sent me:

My understanding is that mac OS 10.13 is a 64 bit OS, and so should be compatible with a build published using the osx-x64 command. So I suppose the straightforward question to ask is “Is Monogame 3.8 compatible with OSX versions earlier than 10.15, or is that the cutoff point?”.

Note: I don’t personally have a Mac and don’t know anyone who does. I’m trying to compile everything on a Windows pc and work with the player who sent me this screenshot to get it running.

Note 2: this isn’t the only Mac user who has noted the mac build as not working, so there may be additional issues, but this is the only one who has given me actionable info on the follow up.

My deployment process:

Step 1: Publish my game using this command

cd "C:\Users\Quasar\source\repos\Species\Species"
dotnet publish -c Release -r osx-x64 /p:PublishReadyToRun=false /p:TieredCompilation=false --self-contained

Step 2: Rearrange the published files into an application bundle under species-app:

robocopy /E /DCOPY:DAT bin\Release\netcoreapp3.1\osx-x64\Content bin\Release\netcoreapp3.1\species-app\\Contents
robocopy /E /DCOPY:DAT bin\Release\netcoreapp3.1\osx-x64\publish bin\Release\netcoreapp3.1\species-app\\Contents\MacOS\
rd /s /q bin\Release\netcoreapp3.1\species-app\\Contents\MacOS\Content\

Step 3: Copy a correctly structured info.plist file into place.

xcopy /Y Info.plist bin\Release\netcoreapp3.1\species-app\\Contents

Step 4: Deploy the contents of \species-app\ to steam.

So, I open this question to to floor. Anyone know what it is I’m doing wrong here?