There's an interesting blog post on this subject (likely someone posted it already): https://dkb.blog/p/google-search-is-dying
I find it to be very agreeable. Search is dying and I don't agree that appending "site:reddit.com" is any kind of permanent solution, just a workaround that will also break.
Modern ticket system or issue tracker? Yes, absolutely. But Jira? Certainly not, considering Atlassian's business practices. A project like Linux deserves a system where they can maintain some control and it probably should be open source.
Yeah email is ancient and certainly terrible from a usability perspective if you're an outsider to the workflows, but at least it can't be shut off or taken away on a whim. Also it's universal and therefore accessible.