You may want to ask support (@gopher.ny, @bobbyD) to look at your hub to see if they have any suggestions.
I think it's time for a soft reset. Backup file sizes on the hub are small, nowhere near what a real database of this size would generate. I believe the database is corrupted. Take a local backup, too, just in case.
I followed the linked instructions for a soft reset exactly. Now, my hub is broken: when I click to restore a local backup, I can do so, but as soon as the restoring backup screen goes away, I'm left on the backups page with nothing happening.
I wish I hadn't done this reset. This is so annoying. I did think that Hubitat would be a learning curve, but things simply not working as they should is not what I expected.
What happens if you go to hub's home page, http://your.hubs.ip.address/ ?
The hub responds to support tool's requests, and there's a small database file present on it.
If that shows no information, try restarting the hub (yes, I know...) and restoring again. It made a new (perhaps empty) backup, but there are earlier daily backups sitting on the hub, too.
The page I get is the get started page. I then click on restore backup at the bottom, but when I then restore a backup, nothing happens. If I then go to my Hub's IP address in a separate tab, then I reach the getting started page again...
How do I restart the hub now - unplug it?
A better way to do it is from diagnostics tool, same one you did a Soft Reset from. Reboot is one of the options there.
I've tried that... How long is the "your hub is starting up" screen supposed to take?
Shouldn't be long. It's up and responding to the support tool again. What do you get in the browser?
I've still got the your hub is starting up screen...
And when I go to the IP address in a separate tab, I get the "get started" screen...
Does it allow you to restore from a backup after the reboot?
I tried again, didn't work. Then, I uploaded a local backup that I had downloaded before, and that has now worked - hub is rebooting...
OK, that worked...! Thank you for your help!! I have to say support is really amazing!