If ssm-session-manager-plugin gives you a shell, then it should not be too hard to extend Tramp to use it directly. (I know nothing about ssm-session-manager-p

If ssm-session-manager-plugin gives you a shell, then it should not be too hard to extend Tramp to use it directly. (I know nothing about ssm-session-manager-plugin.) Tramp does not need scp to transfer files, it can just as easily multiplex them over the shell connection by using base64 or uu encoding.