Per current documentation to deploy your extension to the marketplace you should use the following command:
tfx extension publish --manifest-globs vss-extension.json --token [token]The [token] here is the Azure DevOps personal access token with the Marketplace (Publish) scope and access set to All accessible organizations.
Note that the instructions say to use a global PAT, but the UI doesn't allow one to select this GUID.
This small tool will help you create a global PAT that will help you publish your extension. Be careful when using personal access tokens with broad access across the organizations you have access to.