Ubuntu 20.04 often freezes before login. Error with /etc/profile

Question

I am quite new to Ubuntu. For a month, my system has frozen 2 out of every 3 times when it reached the login screen.

Dual boot with GRUB was fine. Keyboard was responsive and I could switch between Ubuntu and Windows.

With "nomodeset", all the kernel messages were invoked and carried out neatly. After that, four scenarios happen:

• A pitch black screen.
• A purple screen is shown but no login box follows. No mouse is found.
• The purple screen showed up but no login box was seen. Mouse is seen but either stuck or moveable.
• The purple screen and a login box is shown. I typed my password, hit enter, saw the login box disappear and the monitor was stuck with the purple screen.

Of all cases above, no error message appears. I could not access TTY.

At first, I thought there was something wrong with GNOME display manager. I reinstalled gdm3 and the freeze still persisted. I switched to lightdm, successfully got past the login screen and found the error message below.

Found when loading /etc/profile:
:: ERROR: Unable to proceed: possible causes listed below.
This script must be sourced. Did you execute or source this script?
Unrecognized/supported shell (supported: bash, zsh, ksh, m/lksh, dash).
May fail in dash if you rename this script (assumes "setvars.sh").
Can be caused by sourcing from ZSH version 4.x or older.
As a result the session will not be configured correctly. 
You should fix the problem as soon as feasible.

I tried:

$bash /etc/profile 

and was hit with another error:

:: initializing oneAPI environment ...
   profile: BASH_VERSION = 5.0.17(1)-release
:: ERROR: No env scripts found: No "env/vars.sh" scripts to process.
   This can be caused by a bad or incomplete "--config" file.
   Can also be caused by an incomplete or missing oneAPI installation.

My machine a Dell Precision Tower 5810, with Intel Xeon E5-1607 v4 and NVIDIA Quadro P600. Dell stated no support for Ubuntu 18.04 and 20.04 on Tower 5810. A month or two before the freeze first happened, I removed cuda11.5, installed cuda11.6 using APT packages and installed Intel oneAPI using Intel oneAPI Base Toolkits. Intel oneAPI has its own version of setvars.sh. I believe that was the most recent installation that had anything to do with configuring the hardware. The full content of /etc/profile is posted below:

# /etc/profile: system-wide .profile file for the Bourne shell (sh(1))
# and Bourne compatible shells (bash(1), ksh(1), ash(1), ...).

if [ "${PS1-}" ]; then
  if [ "${BASH-}" ] && [ "$BASH" != "/bin/sh" ]; then
    # The file bash.bashrc already sets the default PS1.
    # PS1='\h:\w\$ '
    if [ -f /etc/bash.bashrc ]; then
      . /etc/bash.bashrc
    fi
  else
    if [ "`id -u`" -eq 0 ]; then
      PS1='# '
    else
      PS1='$ '
    fi
  fi
fi

if [ -d /etc/profile.d ]; then
  for i in /etc/profile.d/*.sh; do
    if [ -r $i ]; then
      . $i
    fi
  done
  unset i
fi