I'm a long time Linux user but by no means an expert. I'd become complacent with my Linux installs and was still sitting on Mint 18.3 (Mate) from 2017 - . I thought I could jump straight to the latest 21.3. Noooo!!! I had to use the command line upgrade manager to move to 19.0, then GUI to 19.3, then command line to 20.0 (manually fix GRUB), then to 20.3 and then to 21.0 and finally 21.1 but by the time I got there there was no data or user programs left and many things didn't work. Yes, just like Windows I should have done a clean install but I wanted to see how this went in Linux instead of Windows. I was totally frustrated and underwhelmed. There may be a way to drop a 21.3 DVD in a 18.3 machine and come out the other end with a 21.3 machine and all the customer data and programs intact but I don't know of it and couldn't find it with immense Googling. Mint does have Timeshift included and I'm restoring back to a save around 19.1 (or even 18.3) and will go from there again. Regardless, this all humbles my Linuxness.......