The Stable channel has been updated to 73.0.3683.88 (Platform version: 11647.104.0/1/2/3) for most Chrome OS devices. This build contains a number of bug fixes and security updates. page 
I tested access to the Chrome OS Downloads folder that I previously shared with Linux and observe that I can now access the folder, open, and edit files from Linux terminal. Therefore, this release appears to resolve the issue that I observed in Chrome OS Version 72.0.3626.122.
I have found that file/directory sharing is available to all containers and not just penguin. Consequently, I can access the Chrome OS Downloads folder in penguin and fjmdocker.
This release also expands directory sharing to Google Play and Drive. AboutChromebooks
Can now run AppImage packaged applications, which means I can run the Linux version of Standard Notes in Crostini.