1. Issues that can be linked to other issues (regardless of repo), i.e. local issue blocked by remote issue
2. Projects that can contain issues from multiple repos, even a mix of public and private repos
Please say this is now possible, otherwise we too are looking at Linear, Jira, etc when we'd like to be looking at Github.
Due to #1 our org created a no-code repository for hosting all of our issues and it's worked out pretty well - PRs reference the ticket using the issue linking text above and it all works pretty seamlessly - the only slight hiccup is that we only write issues in the no-code repository since splitting issues across repo would cause milestoning issues for releases.
I'm really glad subtasks is now a thing!