I initially Installed Ubuntu 18.04. I wanted to try Ubuntu Studio to use for audio production. So, I backed up and installed Ubuntu Studio 20.04.
Then, I uninstalled Ubuntu Studio 20.04 referring Uninstall Linux from Linux, re-partitioned using GParted (dragged across unallocated space), selected start up options F2 on start-up and tried to remove Studio option at start-up.
Now I can't seem to start up Ubuntu at all. As now all I can see is GNU GRUB v2.04 screen that means nothing to me.