I have a fully-updated 3821X - Streaming Stick 4K+ plugged into an LG C2 4K TV. All Roku apps overscan the picture. This is not a TV setting issue. I have the Emby app installed on both the Roku and my TV's OS. Both have identical picture settings. Here's a test video in the TV's Emby app:
Here's the same test video at the same timecode in the Roku's Emby app:
As you can see, all sides are cropped on the Roku, with it being especially bad on the left and right sides. In case you're temped to blame Emby, here's a screenshot from the Roku's Youtube app showing a timer in the upper-left corner being cropped:
This issue has been posted about repeatedly, but no solution that has actually worked has ever been offered:
Roku Player Cutting Off Edge of Picture. Solutions tried, still not fixed.
How to fix Roku zoomed in and cutting screen off?
Roku Express YouTube app is cutting the edges of some videos
Again, this is not a TV setting issue -- there isn't even a setting on LG C2s to overscan or zoom at all -- and there is no setting on the Roku itself to turn this off. Additionally, I tested an Amazon Fire TV in the same HDMI port and did not have any issues.
Can forum support here submit a ticket to the developers? From my experience and those linked in the above posts, this is clearly a bug that affects multiple models that needs patching.