The answer as of today is that currently it is not supported to deploy commerce SDK CSU package through Azure DevOps release pipeline. The reason is that you can see in the code, AxUpdateInstaller.exe and a topology file. This program and config files are used for updating FnO (Commerce HQ) only. On a development machine we have pre-installed a Retail Server/Channel Database that uses the legacy Retail SDK construct.
The legacy Retail SDK construct can be bundled inside of the FnO installer construct because all custom code is layered over top of OOB code. These pre-installed components are not compatible with the Commerce SDK independent packaging framework.
Secondly when the commerce SDK is compiled/build an installer.exe file specific to that extension code project is created. This installer.exe is what needs to be executed to apply the extension code, not axupdateinstaller.exe.
Packages built with the Commerce SDK, can only be uploaded to LCS or installed against a Sealed Self-hosted CSU installation.