Low Disk Space on Filesystem.root Ubuntu

I keep running low on disk space on my Ubuntu install, and I'd like to fix this without reinstalling / losing data (this is the laptop I use for class and I have all my dev environments working etc, so I'd prefer not to have to set everything up again). I see some other questions related to this, but I'm not sure how specific the solution will be to my system or set up.

$ lsblk
sda      8:0    0 465.8G  0 disk 
├─sda1   8:1    0   100M  0 part /boot/efi
├─sda2   8:2    0    16M  0 part 
├─sda3   8:3    0 203.6G  0 part /media/calvin/967071017070E8FF
├─sda4   8:4    0 238.2G  0 part /media/calvin/Linux
├─sda5   8:5    0   499M  0 part 
└─sda6   8:6    0  23.4G  0 part /var/snap/firefox/common/host-hunspell

$ df -h
Filesystem      Size  Used Avail Use% Mounted on
tmpfs           1.6G  2.6M  1.6G   1% /run
/dev/sda6        23G   22G  431M  99% /
tmpfs           7.8G  425M  7.4G   6% /dev/shm
tmpfs           5.0M  4.0K  5.0M   1% /run/lock
/dev/sda1        96M   31M   66M  32% /boot/efi
/dev/sda4       239G   97M  239G   1% /media/calvin/Linux
/dev/sda3       204G   37G  168G  18% /media/calvin/967071017070E8FF
tmpfs           1.6G  8.1M  1.6G   1% /run/user/1000

Disk Usage Analysis screenshot: https://i.stack.imgur.com/Gxblf.png

A similar question I came across: Low disk space on Filesystem root despite having plenty of space in `home`

Could someone point me towards the best/correct method of fixing this? Let me know if there is any more info I can provide that would be helpful.

The minimum system requirements for Ubuntu Desktop call for 25GB of space for the root file system.

Your current root partition is 23GB. This is insufficient to meet the minimum requirements.

You have several other partitions with free space but this free space cannot be utilized by your root file system because the space is on a different partition.

You should make sure your backups are in order, then repartition the disk, which will erase all of the data. Then reinstall the operating system.

Even though the minimum requirements are 25GB, it would be wise to allocate more space if you don't want to have this problem again. Depending on how you use your system, this 25GB could fill up easily.

You don't need to add any extra partitions to install Ubuntu. The installer will create additional partitions if required.

If you are not planning on sharing data with any other operating system installed on this device, then it's probably not a very good idea to create data partitions if your only reason for doing so is for organization. Use folders for organization, not partitions. This will ensure that free space can be utilized effectively. Otherwise, partitioning creates hard, inflexible limits on how the space can be used. If you're not sure, use the default installation options.

just FYI to anybody dealing with a similar issue, I was able to do fix this using a Gparted Live USB: https://gparted.org/liveusb.php

I wouldn't recommend going this route unless you're tech savvy and are adamant against re-installing Ubuntu, as it was a bit of a hassle, but if you follow the instructions to create the Live USB (I found it easier to create the USB on Windows than on Ubuntu), then boot from the Live USB on your Ubuntu machine, and then follow the set-up instructions for Gparted, you can move / resize your root partition and un-allocated space partitions as you please. I think this method is a bit more risky, but I was happy with the results.