Thank you for the suggestion. I added some usage data to the post. Initially I actually thought that could be about memory or cpu usage, a browse (Firefox, looking at you) or whatever issue (including touchpad, not totally discarded option so far), but seems not to be the case. I still have to find something concrete.
In fact, I am now used to stop everything I am doing (especially YouTube videos, etc) and stare at some monitor (going to add iotop) during updates. Basically, to update is not a pleasant experience anymore…
I start to think that could be something related to kde/plasma, even if not the same case, as a few times it started to complain that could not recognize (I do not remember exactly now) the display, custom shortcuts, xclip and some other things stopped to work all together. Generally a log out/ log in solved the issue.
Also, in my case it seems to be related with 20.09, as I started with 20.03 and never had issues before changing release.
As you said it also happens in “pure” i3, I doubt plasma is to blame.
Though your CPU is a bit older than mine (i5-4210M CPU @ 2.60GHz), and I do recognize occasional slowdowns as well.
Usually those are accompanied by increased CPU usage and high core temperature. Those happened a lot less since I cleaned the cooling related parts (which I do about once a year), especially the radiator is always blocked by dust.
This is why I asked you to monitor actual clock rate and temperature. When overheating my CPU clocks down to 800MHz and wont go over 1GHz before a certain threshold is reached again.
And of course when in this overheating mode, several freezes occure, in worst case up to the point where the BIOS just kills everything as the heat spreads throughout the system.
To clarify, I said even if not the same case: with i3 I am pretty sure that I experienced one of the first freezes (as they happened months apart, I am not sure of the sequence). Not blaming, but pointing out that the xclip, shortcuts etc is exclusively a plasma thing. Perhaps that has nothing to do with the issue.
That should lead to a shutdown, right? Or could just freeze the system with the need of a hard reboot?
Yeah, that would lead to a shutdown, though I experienced minute long freezes, during which I wasn’t even able to connect via SSH.
Usually I do a hardware power down after 5 to 10 minutes. Though during remotely updating I got dropped out from SSH, and my son reported that my laptop was on full fans for an hour before it went out.
So, have you already monitored temperature and actual click rate?