I'm on Solus Plasma. It's worth noting that this never happened on Solus GNOME which I was driving for a few months before switching to KDE.

So this doesn't happen every time I shut down, but it's pretty frequent. What usually happens is I initiate shutdown (using either KRunner or from Application menu clicking shutdown). The monitor and keyboard and mouse switch off, but the CPU does not. Fans are running, RGB is on. I can't wake it up with any keys. I can only long press power button on the cabinet to force shutdown.

Couple of things I observed:

1. I noticed sometimes my external HDD was not auto mounting when I started the PC, so I thought maybe it was automount that was preventing shut down also. So I tried to see if the times automount didn't work, coincided with the times I had to force shutdown - they don't. Even if it shuts down without issues I sometimes notice automount not working. And not every time I force shutdown I have automount issues.

2. I thought maybe clicking the shut down immediately button on the confirmation screen is what is causing the issue. I tried letting it shutdown on its own after the 10s countdown, but that also yielded inconsistent results.

I'm at a loss for what to do now.