Kubuntu 21.04 – KDE frequently becomes unresponsive

I have an old Compaq Presario CQ60. This was running Windows Vista when I obtained it, but I’ve since switched it to Kubuntu 21.04. It should be noted that when I tested Vista, it worked fine. The switch was to go to an OS that was a bit more modern, and to remove any crud from the previous owner.

The problem that I have is that KDE regularly and randomly becomes unresponsive. By unresponsive I mean the mouse moves, yet clicking on anything has no effect. Keyboard input is ignored. When this happens, the only course of action is to hit the power button to switch the machine off and then reboot it.

I’ve switched over the compositor from OpenGL 2.0 to XRender. For a brief while this appeared to help. I’ve tried enabling the CTRL+Alt+Backspace key combination to kill the XServer session. When it’s locked up, that key combination does nothing.

It is impossible to check resource usage because there is no way to get to a terminal or other application with the machine not responding to keyboard input or mouse clicks. It is entirely possible it’s related to RAM usage (it has the required 2gb minimum, I’ve got an upgrade coming, just need to wait for it to arrive) but it’s really difficult to say that with any certainty at least until I can get it upgraded. Having said that it can be as little as 30 seconds after login before the whole thing becomes unresponsive.

As mentioned earlier, running this on Windows Vista appeared fine so it looks like its related specifically to the KDE installation. And yes I know the machine is a little bit old, the whole purpose of the machine is as a portable word processing box so it hardly needs to be a powerhouse and I’ve always considered Linux a great option to extend the life of older hardware.

Is the limited RAM situation likely to be the main cause of this, or are there other things I can investigate?