How to Github azure/publish action fails to start app?

Hello,
I've spent 3 days going around in circles.

• have a repo that contains a SOURCE/ folder
• within which is a *.sln that in turn references an App.Host/App.Host.csproj
• which is a .net 8.0 asp.mvc app, which
• locally it builds and runs.

THe repo contains a .github/workflows directory containing
a deployment.yaml file.

THe yaml file contains steps that

• dotnet restore <subdirectory> --configuration release
• dotnet build <subdirectory> --configuration release
• dotnet publish <subdirectory>
• azure/webapps-deploy@v3
  with: startup-command: dotnet App.Host.dll

Workflow is Happy
It goes green showing it has built the remote Resoruce Group, the App Service Plan, the App Service
Then done the steps to restore/build/publish/deploy the code to the target app service.
The app Service is an average tier/cost one of linux with fx set to netcore:8.0

Files were published:

Later, when using mkudo interface can see all the files (dlls, etc.) in the wwwroot/ directory.

But not running
But when i go there, I see only a "Your web app is running and waiting for your content".
Doesn't matter how long I wait (5, 10 ,20 minutes)

At least the dynamic aspect doesn't work
I can access a static *.html file that I put in there to test.

App Configuration/Startup up Fiddling
Back in Azure, I fiddled with startup command of the App Service to try different variants

 startup-command: dotnet

 startup-command: dotnet App.Host.dll

 startup-command: dotnet /home/site/wwwroot/App.Host.dll

and restarting -- but to no avail.

See Failures in the logs

In the logstream i see:
... [INFO] Could not find build manifest file at '/home/site/wwwroot/oryx-manifest.toml'
...
... [ERROR] /opt/startup/startup.sh: 13: /opt/startup/startup.sh: dotnet: not found

But i don't know what influences this stage or outcome so don't know how to fix it.

Errata

I noticed earlier that if I set the linux fx to netcore|latest...it set itself to provide .net.core 6. and failed to run the app. By being explicit with the version it's now 8.0, so compiling, publishing, ...but not running for unknown reasons.