From 18.10 ? This is 19.04 thread ? Did you upgrade from 18.10 ?
Did disabling the dimming work for you ? Dimming is broken on many new hardware and not an unity specific issue.
Usd seems trying to set input device and fails when lockscreen is still idle may be a delay from intel hid. Other than that not much useful information. Do you have synaptic driver installed? If so uninstall it and reboot. Only use libinput driver.
When was the last time it worked for you? May be you check booting into older kernel if it is the same.
Do not use purge command on gnome. There are lots gnome libraries that unity depends on.
What do you mean by moving home folder? ~/.config or ~/.local/share in older version won’t be compatible with newer version. Instead use a 2nd partion, install Ubuntu dual boot and move only Documents and other personal files. You can still move folder inside .config selectively.
If possible please try with persistent live usb and install minimal unity on it and check. I will ask @dale-f-beaudoin to update the iso.