Late 2013 27" iMac endless kernel panic boot loop, no recovery mode, no safe mode. Could this finally be the end?

Hi gang.

My stalwart, long suffering, incredibly trusty iMac may be knocking on death's door.

It is a late 2013 27" iMac, running the latest version of macOS Catalina 10.15.7. 32GB RAM, Intel Core i7. 1TB SSD. Model A1419 (I think).

Today it hard crashed to a kernel panic. Tricky to explain, but the crash felt a lot 'scarier' or more... serious than a standard crash. It was clunkier, took longer, and the OS truly locked up, and then flickered out with some weird graphical glitches. Very grim.

Following the crash, the iMac started a reboot loop, ending with a kernel panic after the Apple logo progress bar hits about 75%. This is repeatable and what happens now every time the computer is powered on.

Note that the FIRST time the iMac attempted a reboot, the Apple logo/progress bar had a visible graphical glitch a handful of times before hitting the kernel panic. I haven't seen the graphical glitch since.

Here's what I've tried so far, with no luck:

• Boot into Safe mode: no dice. Progress bar fills to 100% then stops. No further.
• Boot into Recovery mode: no dice. Progress bar fills to 50-60% then stops. Doesn't go further.
• Boot from bootable installer drive: no dice. I created a brand new bootable drive with a fresh download of Catalina. I could get to the drive selection screen, but after selecting the boot drive, the progress bar takes me to 50-60% and then stops. Nothing further happens.
• Boot from internet recovery mode: no dice. I got the globe with the progress bar. Progress bar fills to 100%, then the system restarts with a chime. Then I get a progress bar to 50-60% which triggers a kernel panic, and then an endless boot loop.

I think that's pretty much it in terms of trouble shooting options.

I am going to attempt to access the SSD tomorrow via Target Disk Mode, but I don't have high hopes. All my critical files and projects are safely backed up (thank you Google Drive/Filestream/CloudHQ + AWS) + local external copies, and 90% of my other sundry files, documents and other bits and pieces of data on the iMac are also all totally fine. I've been expecting the iMac to die for, like.. A few years.. So I've been pretty meticulous with backups. But I'd still like to be able to access the SSD if I can, because I'm sure there are some bits and pieces of data lying around that might have not been included in my "big important directories get backed up but maybe don't worry about all the crap in your downloads folder" protocol.

I have an appointment with the Genius folks on Monday to get an official diagnosis, but I thought I'd see if anyone here has any thoughts.

Any help or insights would be appreciated.