I just read an interesting post by mdooley in the tips and tricks section of this forum and it's about having a operating system installed with a separate data partition and using links between the directories in /home/username/ to folders with the same name in the data partition. I have been hanging around here for a while but this is the first time I read that one. That seems like a great idea to me. We have 'make link' in our right'click menu in Ubuntu MATE, so this would be very simple and easy for anybody to set up. Install Ubuntu-MATE Using A Data Partition - by mdooley
Then when we have our operating system separated from our data we only need around 20 or 25G of disk space for the operating and all our installed software along with our bookmarks and settings and stuff.
There are quite a few ways to make a backup of the entire OS with all its installed software and settings. The LVM snapshot idea is probably the quickest and easiest in my opinion, but I had to invest in the time it took me to learn LVM and become confident with it. GParted is great nowadays, we hardly need LVM anyymore. It's not too difficult to copy and paste partitions around with GParted, but you might have to edit /etc/fstab if it gets given different file system UUID number and re-install GRUB to get the restored operating system booting again. There's also an application called partimage which I remember practicing with a long time ago and that should do the job too. Probably there are a few more solutions we could add to the list.
Whatever options a person might choose, remember a backup is not a backup unless you have practiced how to restore from your backup and you are confident you have the required skills and it's going to work.
It's a good idea to have a test installation on some separate disk or disks and practice backing up and restoring it, so if you ever have to do that to your real OS you'll now what to do, kind of like doing fire drills. One of the great things about free software is we can install as many copies of it as we want if we have the disk space.
My new 1TB SSDs are still coming in the mail and I'm looking forward to getting them. They only cost me about $140 each, (Australian), that's only a little over the cost of a tank of fuel for my car these days, or about the price of a new tire.