Ahh, I see! Yeah, I am on shared hosting, but still have Cron (in my DirectAdmin panel, under advanced, but it's there), and most of the shared host I have seen here in The Netherlands have it enabled too. So that's why I took this cronjob approach first.

I totally agree the image looks hacky, but your starthook runs on pageload, right? Then you're just moving the work to the next request, which is even worse than doing it inline. (A person sending a webmention knows what it's waiting for, but the person who visits the homepage right after a webmention was requested just thinks the site is slow.)

The whole point about a queue is to get work out of the pageload, into a separate process. Any solution that triggers with a panel hook, within a plugin, etc, will defeat the purpose of the queue.