☺ I got sick of Windows and switched to Linux on my Lenovo ThinkPad T420 two months ago. After trying a few distro/flavors I settled on Xubuntu 18.0.4. It was always a little buggy with random program crashes and errors, but it worked fine until last night.
When I rebooted last night, it asked me to unlock my disk and log into my user acct, then it went to a flickering white screen. I did a little research and figured the problem was "LightDM" went rogue. So I purged and reinstalled it … same thing. I kept reading and found the problem could have been proprietary Nvidia drivers. I tried to purge them from recovery but got some "system is in read-only mode" error, even with sudo.
I rebooted again, and now my laptop doesn't even the Lenovo boot screen. It boots straight into a solid white screen. I tried pressing buttons to get to the boot menu, and they made their usual noises, but the screen stayed white. Please help me! I'm starting college in 2 months and don't have money. Thank you so much in advance.