What is the "On My Mac" folder in macOS Big Sur?
Solution 1:
In Big Sur, ~/Library/Containers shows in Finder as ‘On My Mac’.
This is a trimmed down version of the Documents from each of those containers, only showing apps which open their Documents on macOS like iOS for visibility in the Files app.
- https://georgegarside.com/blog/macos/macos-big-sur-hidden-features/#finderapp (my blog)