Nevermind, I used a thinkpad t470s plus an external ssd which I could wipe out and install ubuntu mate 18.04 32bit on it. To reproduce I enabled the HWE ppa and upgraded mesa, then installed linux-generic and booted 4.15.0-55. It ended up with a mostly blank screen but keyboard had no effect other than the power button.
Then I installed 'linux-image-4.15.0-56-generic linux-modules-4.15.0-56-generic linux-modules-extra-4.15.0-56-generic' and rebooted, and now I got to the display manager normally.
Nevermind, I used a thinkpad t470s plus an external ssd which I could wipe out and install ubuntu mate 18.04 32bit on it. To reproduce I enabled the HWE ppa and upgraded mesa, then installed linux-generic and booted 4.15.0-55. It ended up with a mostly blank screen but keyboard had no effect other than the power button.
Then I installed 'linux- image-4. 15.0-56- generic linux-modules- 4.15.0- 56-generic linux-modules- extra-4. 15.0-56- generic' and rebooted, and now I got to the display manager normally.