Not necessarily. It's still there. To see the available runtimes for Linux you can run az webapp list-runtimes --linux
CLI command. To create a 2.2 web app, you can run az webapp create -n mynetcoreapp -p mylinuxplan -r "DOTNETCORE|2.2"
in a bash window. If you're using powershell, preceed webapp with '--%' ( az --% webapp create -n mynetcoreapp -p- mylinuxplan -r "DOTNETCORE|2.2"
).
However, you can select 3.1 as the runtime in the portal and still deploy your app as 2.2 runtime and it will still function.