See Chromium change log 
So far I have not been able to determine what has changed.
Decided to try accessing a SD card. I enabled the following flags:
chrome://flags/#crostini-usb-support chrome://flags/#Enable Crostini file sharing in Files app
After a restart inserted a SD card into the slot in my USB-C Dock and observed that the SD card appears in Files. I right click and select to enable Sharing To Linux.
I think try to access the SD card from terminal by entering:
cd /mnt/chromeos/removable/SD
And I get permission denied. When I ls the directory I see that it is owned by nobody nogroup.