I noticed there was an update available this evening and decide to install it. After the update, the hub came back up and is currently hung at Initializing Hub: 75%, the LED on the hub is blue. It's been that way for well over an hour, probably closer to two hours at this point.
I can go to http://(hub ip):8081 and I get the Hubitat Update Tool, it says I am currently running 220.127.116.11 and has 3 previous versions that I can switch to.
I thought I remembered seeing a URL that would cleanly reboot the hub and thought I would try that, but I haven't been able to find it. I'm going to search a little while longer, then just switch back to 18.104.22.168 using the Update Tool.
My hub setup is fairly simple, I have 4 or 5 Iris V1 contact sensors, 3 Iris V1 smart plugs, and a Iris branded Linear Z-Wave garage door opener. I've installed Rule Machine, Chromecast Integration (to announce door openings on Google Home devices), and Maker API (so my Home Assistant instance can control a smart plug). I also installed the Yamaha Network AVR Integration from this post: [Release] Yamaha Network Receivers Basic Integration, that's the only non-built in app code that I've installed. Everything was working fine before the update.
This may be just a glitch on my hub, but I thought I would report it in case it's an indication of a bigger issue.