Timeshift. It has an easy to understand GUI that doesn't really need much of an intro: You create snapshots of your system files and configs that can be restored if/when you bungle it up.
Timeshift works best if you use BTRFS for your root partition because snapshots can be taken instantly. I have mine setup to automatically take a snapshot every day.
There are many approaches, depending on what broke. In my case the system was fine, just xorg being completely borked. So I logged into the console and fixed it.
If regular console doesn't work, something really went bad during boot, for which there's single-user mode which is kind of similar to safe mode from Windows 98 (I'm sure there's something similar in newer windows versions).
And of that doesn't work, there's the minimalistic rescue shell.
And if that doesn't work, you can boot from a USB or some other external media and try to fix your system from that, maybe even using chroot to use the system somewhat normally.
Why does Timeshift only support btrfs? Is it just a lack of developers? LVM supports snapshots too, even if you're just using ext4. ZFS supports snapshots too.