GUI crashed? SSH unavailable. Can I restore from backup?

[EricPerl]

You might need to enable logging for the default pass rules in FW settings.

Do you have a multi-WAN setup?
Did you disable the anti-lockout rules by any chance?
Any port forwarding?

Feel free to use your backup at any time... It's your call.

[maxxell]

Do you have a multi-WAN setup?  No.
Did you disable the anti-lockout rules by any chance?  No.
Any port forwarding?  Just one for Plex (not the standard port). I do have a rule for forwarding to nginx, but I keep that disabled. That's what I use the HA plugin for. I can remotely enable that port to use a service when I'm not home (which is rare).

For now my internet and WireGuard are still working, so I don't mind taking some time/effort at diagnostics. But if at a dead end, I am comforted knowing a restore from backup should resolve this.

Anything else you think I should try?

[EricPerl]

If it were me, I would enable logging on default pass & block rule and verify what happens in live view as you try to ssh.
Not seeing anything implies the request is not reaching the interface.

I only know a few things that cause this:
* port forwarding (precedence over FW, especially if the port forward rule is set to pass).
* gateway specified in FW rule (as in Multi WAN)

[cookiemonster]

If you don't mind me saying, you're going in a tangential direction to the problem.
The symptoms are of a hardware problem and those are hardly found on the GUI. The GUI will at best, show you symptoms. Looking at firewall rules and the like won't give you a hint on any underlying hardware problem. For that, you need to enable ssh for comfort, or attach a keyboard and monitor.
What to look for? That's the thing with PCs and *nix-like OSses. You need to start learning how to diagnose.
Start with dmesg (system buffer). Older logs too, as the buffer starts (latest.log) only from last boot, but previous are alongside it.
Then look around all other related logs.

[maxxell]

you're going in a tangential direction to the problem

I tend to agree with this.  It doesn't seem like there's some esoteric setting blocking SSH.  I think I've had a glitch/failure of some kind.  Someone on reddit mentioned the possibility of the SSD being filled up by logs, though none of the attempts to clear logs has helped.  Maybe the plugin I installed lately caused the hard drive to fill, etc.  Without SSH (or convenient console) access, I am in a severely limited state - to only what the webGUI can do. 

Fortunately, it's still FUNCTIONAL, or this failure would have been immediately been met with a reinstall and restore from backup.  Strange as it is... 

At this point, though, I think it's time to restore from backup and see whether that brings back functionality.  I may wait until after upcoming vacation though, in case the restore from backup only makes things worse somehow...

[maxxell]

Well today I finally got around to restoring from backup.  I had to walk away after clicking "go" but when I got back I saw a message about OPNSense is rebooting.  Unfortunately, the dashboard was still broken.

I never actually saw it reboot, so later in the day I use the webGUI to force a reboot.  Although I still didn't actually hear the reboot beep, so maybe it wasn't actually rebooting...

So I walked over and pulled the plug.  When it came back online, the webGUI was feeling better.  I had all my dashboards back.  I was able to check for, and perform, available updates.  When the updates finished, I did hear the device beep for reboot and got all my dashboards back afterwards. 

Situation resolved, I guess.  Thanks to everyone that offered suggestions.  I will pull another backup now, just in case this is preparatory for catastrophic hardware failure.