Currently, apps can only be accessed by users in the workspace where it is deployed.
One workaround solution, depending on the amount of external users you want to grant access to, would be the following:
- Create a new workspace.
- Add external users to the account and assign them only to the new workspace.
- Deploy the app within the workspace, and restrict the added users to only be able to view the app. Lock everything else down in the workspace.
I wish there was a better solution, and maybe someone else can chime in here. This solution does have risks, but with the limitation of needing users to be within the account to be able to view the apps, a workaround is needed.