Hi Robert,
Thanks for trying External Share and for the feedback, that helps a lot.
Sharing for linked work, subtasks, and attachments does work, and plenty of our customers use it every day. When those items don't show up in a shared link, it's usually a settings thing: the toggles have to be turned on for that particular share, and attachment visibility can also depend on the issue's permission scheme in Jira.
We'd like to get it working for you. Open a ticket with us here and we'll look at your exact setup: https://apportunity-apps.atlassian.net/servicedesk/customer/portal/1. Happy to hop on a quick 15-minute call too and walk through the sharing options with you.
Once it's sorted, we'd appreciate it if you'd take another look at your review.
Thanks again,
The Apportunity Team