This is a known issue, but isn’t something that we are able to resolve, unfortunately. The problem is caused by Steam Overlay’s incompatibility with CoreAnimation layer we use to display the window (which is required for Metal, so we cannot go back to old code that doesn’t use that). Valve is working on a fix for this, but they don’t have ETA.
Here’s a link to the original Answerhub post that reported this issue:
If you’re working on Windows, it should work fine. As far as Mac goes, I’m not a Mac user myself, so I can’t say for sure that it’s working. But if you are still having issues with it, I recommend reaching out to Valve for further support on this since it has been determined to be an issue on their end.