Set a catch-all to "Deliver locally, to mailbox root"
After saving the rule, it will be added to /etc/postfix/virtual with a mapping to the root mailbox (root is just an example here)
Go back and edit your catchall, uncheck the "Deliver to local mailbox" option and instead check "Forward to mailbox" and type in "root". Save the modified rule.
Look in /etc/postfix/virtual and you will see that the rule is broken and has not updated. The only way to get rid of it is to delete the whole catch-all and re-add it with the delivery option you wanted. Modifying existing catch-alls is unreliable.
[MAIL ALIAS] Writes incorrect values to config file