No keyboard on Raspberry Pi 4 8Gb RAM Ubuntu 64bit
I have a similar problem with Ubuntu 21.04 64-bit on a Raspberry Pi 4 B with 4 GB memory, using a Logitech K780 Keyboard on USB, or Logitech K260. Both keyboards were on a Logitech Unifying Device USB key.
I installed Ubuntu 64 by using rpi-imager in Raspberry Pi OS to write Ubuntu to a 16 GB SD card and then booted from the card.
It is not a keyboard problem because the keys work OK until after I log in,
After I log in, each application window comes up under a clear window that shows the entire application window but prevents any keystroke from falling through to the application window. Both windows show the 'X" close button but only thee top button works, and it closes both windows.
If, before logging on, I click on he round icon in the lower right corner, and choose "Ubuntu on Xorg" from the resulting menu, I can log on and get a desktop that works normally with the keyboard.
My guess is that the icon in the lower right corner of the login screen selects between two sets of desktop options. The default set fails and the other set works.