Same issue here. I have an on-premises gateway and SQL server, so I was able to run SQL Profiler and see the UPDATE statement that PowerApps generates -- it does have an OUTPUT clause without INTO clause.
Essential piece of functionality with a tool like PowerApps to be able to use triggers on the target data source. Surprised this is being treated like a feature rather than a Bug.
Any clues on timeline for this. It's a bit of a showstopper for us as we really don't want to be introducing messy workarounds to this.
We were excited when initially looking at PowerApps, then ran into the trigger issue on a simple app. That stopped us cold. Hopefully it gets resolved.