2009 iMac boot stuck at "End RandomSeed" -- Apple logo with no progress bar during boot

I have the exact same problem as this thread: https://discussions.apple.com/thread/250398584 except under different circumstances.

My late-2009 iMac had a bad hard drive. After letting it sit for a long while (years), I finally replaced it with an SSD. After I replaced with new SSD, I tried booting with an external bootable backup. I only got an Apple logo without a progress bar. I have done the following:

• Replaced PRAM battery
• Baked my video card as shown here to rule out video card issue
• Reset NVRAM
• Booted with original installation CD
• Booted with new Mac High Sierra installer

Nothing has worked. It's still showing just Apple logo with no progress bar. After booting in Verbose mode, it shows the screen below, exactly what was experienced by @kerr810. I have no third-party accessories attached to my 2009 iMac, just Apple's own bluetooth keyboard and mouse.

Any ideas on how to get this fixed?

Thanks!