The only other info I managed to find was these instructions.
https://unix.stackexchange.com/questions...ubuntu-kde
As solution for this
https://askubuntu.com/questions/824339/m...untu-16-04
Which this second link also contains a temporary solution the person used previously, to restart the lightdm and as it needed to be done often, the user shows how they changed lightdm to gdm instead, and this solved it for them.
Edit - Just for experimental reasons, do you have 2 usb mouse you can plug in to use one after another, so both are connected at same time ?
Does the second mouse cursor display ?
I made some edits to stop my mouse working, which made it also so it didn't work after reboots, and was not recognized if removed and reconnected, when adding an alternative mouse it also didn't work.
But when leaving first mouse connected and also connecting a second mouse, second mouse work and I changed back the settings of first mouse so it worked.
If it will work for you it may help in looking at settings easier than using the invisible cursor when trying solutions.
Example when both are connected go to Menu>Settings>Mouse and Touchpad then tick enable this device for each mouse in drop down menu, then remove 1 of the mouse, because it seems from the my experiment some fixes require specific sequences for fixing the mouse problems. I don't know why it is so, only that it worked, so it will be useful for some mouse problems, I don't know if it will be solving your mouse problem.
