I am running Slackware-Current, kernel 5.13.13, installed yesterday. For the last 3 upgrades (back to the end of July) I've been having keyboard/mouse problems. Occasionally, the desktop (both XFCE and KDE) will freeze requiring me to restart it. Usually, after rebooting, even from a powered off state, the keyboard is unresponsive at run level 3. keyboard is usually, but not always responsive at run level 4 -- but there's the freezing issue. Sometimes, moving the dongle to a different USB port would permit resumption of keyboard/mouse response.

This problem is worse with 5.13.12 and 5.13.13. Yesterday, after several reboots and power cycles, I could not get the wireless keyboard or mouse (Logitech) to respond, so I plugged in a wired keyboard and mouse. Interestingly, I've had no freezes at all since doing so whereas with the wireless keyboard it froze 6-10 times just yesterday.

I've now checked my wireless keyboard and, without logging off or rebooting, it is back to responding.

I've never had an issue when booting to the installation DVD.

Does anyone have any idea on what could be wrong or where I can look for info. dmesg doesn't show any clues (to me).

FWIW, the Logitech K400r, wireless keyboard/trackpad combo used here didn't have a problem with the 5.13.y series or any series, come to think about. I've been using the the 5.14.y series for the last few weeks.
Well, there was one problem, but it involved the location of the dongle in relation to keyboard. Once I figured that out..... all has been well.

Usually I got malfunctions of my wireless keyboards and/or mouses because their batteries.

BUT, I had a case where a malfunctioning power supply given a lower/unclean voltage on 5V+ output and the USB devices behaved erratically. Apparently the the USB devices are particularly sensible to this 5V+ issues and they start going nuts first.

I've plugged the dongle into powered and unpowered USB hubs. I've tried changing batteries.

In fact, it doesn't simply freeze the keyboard/mouse - it actually freezes the desktop: the clock stops advancing, all "animation" ceases. The screens are frozen, but if I log in remotely the programs running on those screens (e.g. VirtualBox) are no longer running, yet the last view before death remains. I normally recover (from a remote ssh session) by doing 'init 3' followed by 'init 4'.

I'm not so sure it is the fault of the Logitech. However, not having had a freeze all day while using the wired keyboard, and having 6-10 freezes in one day yesterday with the Logitech makes me wonder. I'm now using the wireless and if/when it freezes I'll plug in the wired keyboard/mouse and see if I get response.

Later ...

Interesting. I've run now for almost two days on the newer kernel 5.13.13 with the wireless keyboard and haven't had a single desktop freeze-up. One difference is that I haven't run VirtualBox during all that time. I'm going to fire up VBox now to do some work, so we'll see ...

Ive had several desktop freezes since upgrading to 5.13.13 9 days ago. I had switched to KDE to see if that helped, but no. Sometimes it's happened with VBox running, sometimes not. This last time VBox was running, and the freeze-up occurred while moving my mouse across the panel at bottom to select an app. It showed the pop-up menu when I hovered over it (I think it was konsole), then everything frozen. Shortly thereafter the system automatically went to level 3, then level 4, but nothing on the screen. I did a remote login and rebooted. I wish I had more information. Any advise on where I could look for an "autopsy" would be appreciated. I could possibly boot to DVD and examine log files. Meanwhile, I'm reverting back to XFCE to see if that makes a difference.

Later, same day ...

More freezes. It doesn't seem to matter whether VirtualBox is running or not, or whether I use XFCE or KDE. Most recently froze when attempting to click a link in Firefox (cursor never made to to the link). It worked much better with 5.12.1x, although I do not intend to downgrade. I'll refrain from further redundant posts about desktop freezing until there is something interesting to report.