I have a really odd problem, running Mint Maya on a System76 Panp7.

A few days ago, I tried installing Remmina using the Package Manager. I don't recall the error but it failed. I tried again using command line and I believe it said something about dependencies having dependencies so I gave up and moved on.

Yesterday (having not turned the computer off since, only sleep), Network Manager was not making a connection to ethernet, it would also try and fail to connect to wifi. Opening "Edit Connections" the dialog would popup than immediately close. Weird. I went to restart and the dialog box was a jumble of characters. Very weird.

Now the keyboard responds during bootup up until I get to the login screen, then no keyboard, no mouse. Can't do anything. No ctrl-shift-F2. I have Knoppix on a USB and was planning to restore my cloud backup of all the system files up until a few days ago.

Is there anything else I can check first? If I do restore, what files/folders would likely be the culprit? Thank you.

did you regularly run updates / upgrades on that machine?

Not that I recall, it's been a while since I ran the last update (though I can't be sure I haven't restarted it since then ). Any suggestions on pinpointing the problem before I blindly start restoring?

well, if you can't boot into the machine and you have a full system backup, why, that's what backups are there for, no?

(what i think happened to your machine: not updating it doesn't matter, until you start installing packages. i guess that resulted in a few packages getting updated, aka partial upgrade, and the discrepancy between versions was so large that it just busted your system. in the future, i'd recommend a reboot after upgrades anyway. also remmeber that linux mint uses some sort of double-upgrade mechanism: first you upgrade only one package called "mint-update" or some such, after that comes the actual system upgrade)