Ask HN: Why is integrating external partners to Jira so hard?

I keep hearing the same thing across aerospace/defense and other regulated B2B programs. Even when both companies use Jira internally, the moment a customer (or other external partner) suggests “let’s just share a Jira project,” it turns into a weeks/months-long IT + infosec ordeal… so teams fall back to email + Excel trackers.

If you’ve lived this, I’d love detailed stories. Some conversation starters:

>> What exactly made it hard? (SSO/IdP, user provisioning, domain policies, MFA, VPN, IP allowlists, Atlassian Access, SCIM, contractors, etc.)

>> Is the blocker usually IT, security, compliance, procurement/vendor risk, or the Jira admins themselves?

>> Jira Cloud vs Jira Data Center: which is worse for external collaboration and why?

>> What are the common “policy red lines” that cause a hard no? (least privilege, separation of tenants, auditability, data residency, CUI/ITAR, SOC2, etc.)

>> What workarounds did you end up using instead (shared spreadsheet, shared mailbox, separate “shadow Jira,” Confluence page, etc.) and what broke?

>> If you did make cross-org Jira work, what was the setup that finally passed and how long did it take? If you didn't make it work, what happened?

Context: I’m trying to understand the true root causes and failure modes -- whether this is mostly technical (identity + permissions) or mostly organizational/policy, and what parts are actually solvable.