SSIS Package execution fails when started by user logging in with FreeTDS
SSIS catalog executions impersonate the connected login, so probably correct that it's an auth issue.  Easy workaround is to provision a SQL Agent Proxy for the identity you want to run the package, and configure an Agent Job to run the package, invoking the job with sp_start_job.

This is similar to, but more secure than, using xp_cmdshell to run dtexec directly, or call the package execution procedures from powershell.  In both cases a local identity is used to execute the package.