OP here.
In a previous life I was part of a team maintaining the weekly backup of over two-hundred SCSI disks (sizes two- to three-GB each - that will hint as how long ago this was) on a system with over-1000 logged-in users. This left me as a rather fanatic backup nut.
Some experience gained in those days:
1. If your backup schedule includes the word 'about', as in 'about monthly', 'more or less weekly' procrastination will hit you at the most inconvenient time.
And it
will happen.
2. If you backup, but have not tested your restore procedure to completion, there in an unfortunate accident waiting for you.
3. Try to have at least three generations of backup, on separate (not necessarily different) media. Keep one copy elsewhere. Always.
My current preferences:
1. Before making any possibly-irreversible changes I take a snapshot. (On Ubuntu I use PinguyBuilder(*) and have had occasion to restore from it)
2. For my more-or-less daily PC I have three extra disks identical to my system, which I clone (Clonezilla) in rotation, on a fixed date every month, and then test by booting and running some tests -- on all partitions.
3. For occasional quick tests I backup using a program called 'clone-ubuntu'(**) (works on MX too) which writes '/' and '/home' to a bootable SSD
HTH,
Mike
(*)
https://sourceforge.net/projects/pinguy ... O_Builder/
(**)
https://github.com/thiggy01/clone-ubuntu