In principle, you can have folders in the root file system (/) for data without affecting or damaging system operation (apart from the fact that you risk damaging the file system if you commit an error while attempting to create folders). However, it is not elegant practice.
There is an agreed-upon file hierarchy standard in linux. /mnt traditionally is just ...
To be able to increase the size of your root partition, the empty space must be contiguous (right next to) the root partition.
To do this, you will need to boot from a USB, then using gparted
Move the swap partition as far to the right as possible
Move the /home partition as far to the right as possible
Expand the root partition
Please not that this is not ...
Ubuntu does not use the root user shell by default. Instead, the root is disabled by default. As such there is no 'root shell' shortcut application.
The way you run commands as superuser is by using sudo straight on the terminal directly, and provide your user's password to attempt to use sudo privileges. There is no 'root shell' application in an Ubuntu ...
After trying to remount the partition in the recommended location from the comments I came across a new set of errors which led me to the eventual solution.
I had to run this series of commands
sudo ntfsfix /dev/sda1
sudo umount /dev/sda1
sudo mount -o rw /dev/sda1 /home/steve/data
Now I have full r+w access again. The key here was the sudo ntfsfix /dev/...
Linux works with a system of file permissions for security. Not everybody can edit any file on the system. Only a user that has administrator privileged can edit system files. The first user created after installing the system will have administrator privileges, i.e., is also system administrator. For other users on the system, this privilege must be granted ...
The problem is that you did not use the correct filename.
The system told you that: No such file or directory
WRONG: root@ubuntu:/# grep -i selinux /boot/config-5.8.0-
CORRECT: root@ubuntu:/# grep -i selinux /boot/config-5.8.0-50-generic
I suggest you create a bootable USB disk and put GParted on it. Then boot from the USB, and you should have free access to your disk and its partitions. Of course, as always, make sure you have backups of your data: GParted is a powerful tool, but it can also create havoc if used carelessly. Good luck with the job :)