Got distracted from the stats plan predictably quickly. On the other hand, I've tidied up my DNS records (mostly upped the TTLs from 5 minutes to one day, since I'm fairly confident they're correct), updated the nginx logs to include cache hit/miss and hostname (the first to see if the cache is working (spoiler: not as much as I'd like) and the second because all the hosts go into the same file and it's not clear which request is for shiv host), and verified a couple of sites on Google search console.

First news from the logs: My Windows browser uses IPv4 for one site and IPv6 for another, even though both share addresses. Weird. I'll wait a couple of days and see if it's still happening.