Check if OS is 32- or 64-bit:

uname -m

Find os name and version (one of these should work):

cat /etc/os-release
lsb_release -a
hostnamectl

Find Linux kernel version:

uname -r

Disk space report (in human-readable format):

df -h

CLI suspend (sleep):

systemctl suspend -i

List kernels:

apt list --installed | grep linux-image

Then delete a problematic kernel:

sudo apt remove kernel-name

(where kernal-name is the part before the / in the previous results, e.g. "linux-image-6.8.0-47-generic").

Exit (or re-enter) graphical mode, useful for installing NVidia updates:
enter graphcal mode:

sudo systemctl isolate graphical.target

exit to command line:

sudo systemctl isolate multi-user.target

check what may be preventing suspend/sleep in Gnome, in general:

systemd-inhibit

and specific reasons:

gnome-session-inhibit --list

Make port writeable for Arduino so it can flash connected devices (change port designator to match actual port):

sudo chmod a+rw /dev/ttyACM0