Recently when installing MySQL workbench on a clean Ubuntu 20.04 install I've run into the following error when connecting locally using a stored password: "An AppArmor policy prevents this sender from sending this message to this recipient.."

An AppArmor policy prevents this sender from sending this message to this recipient

This post on MySQL forum suggests its a permissions issue between MySQL Workbench and the password manager. The fix is quick and easy allowing the two to talk to each other.

sudo snap connect mysql-workbench-community:password-manager-service :password-manager-service

The snap store listing does call this out but if, like me, you installed it from the command line you might not notice:

If you use connections, Workbench use Password Manager and ssh to work properly. So it is necessary to give this permission explicitly.

- snap connect mysql-workbench-community:password-manager-service
- snap connect mysql-workbench-community:ssh-keys
- snap connect mysql-workbench-community:cups-control

It's also possible to edit the permissions in the Snap Store UI by clicking Permissions:

Click Permissions