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.imgur.com/33Si8Im.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.