I'm going to do the same later this year as like you my setup is 10 years plus, though I'll re-install Arch again What MB, GPU card etc did you buy? , as I'm out of touch with the latest equipment now, so would be grateful for a heads up

Use timeshift, install it, just chose where you want the backups to be installed, preferably a second HD or SD Flash. Chose when like once a day, week at start up for instance and forget it. Then if you screw up your Linux, just start in console mode, timeshift --restore and five mins later your up and running.

If you want just your data to be copied, then Cron

Both are standard Linux programs, often already installed depending on what Linux you have

Though to late to help you, when you get it working again, install Timeshift, so that instead of faffing around to try and suss out what went wrong, you just start timeshift -- restore from the console and a couple of minutes later you'll have your working setup back. It's saved my bacon quite a few times in the last couple of years, especially when you can't login to your DE.

Grab a second SSD or HD, that way, keep windows in one as it will be probably be supplied with the computer. Add Linux to the other disk, Debian maybe, EndeavourOs much better. ThNo dual boot. And when starting to computer just choose which disk you want to use (F8 or F12 often) and later if and when ready, you wipe the windows HD and use it for backups

Try Lineage. I ran it on my Pixel 3 for about two years when Google stopped updating it. Then when I decided to sell it, just reflashed the Google OS back on it

Like you i switched from about 30 years of windows to Linux almost three years ago, Ubuntu, Mint, Manjaro, Endeavour before ending up with Arch which I find perfect. I also have two PCs running Debian for HomeAssitant setups in two homes but I don't like Debian I sometimes use my wife's Windows setup for Garmin Express as that's the only windows program that I need. So keep on going, Windows is not missed,

First dopey question, what is a NUC? It's probably a computer but? If so same'ish story here went from a Pi4 to a Lenovo Tiny PC (reconditioned from Amazon at 100 euros) then sold the raspberry for 65 euros 🤣 Far faster and better, installed Debian Bookworm, Docker and then did a new Mosquitto and HA supervisor installation. Far better 👍

Timeshift. Easy to set up. Easy to use, only takes a couple of minutes to 're-set' your system back, if you break it. If you want just to backup files, documents etc then Cron. I use both. They are standard Linux programs and easy to use

For note taking, Joplin is pretty good, in fact I went from Simplenote to Evernote (over kill and not free) to Joplin using Dropbox for the syncing (syncing is done by Joplin, so you don't need a 'syncing' app) between my PCs, all Linux and my Android phone. Simple to set up and free. I do not use it as a Journal as that is extremely poor, but for notes, it's perfect

I use timeshift, on Arch and a Debian setup . It's simple to set up, I do a automatic snapshot once a day, so if something breaks, just boot into tty and restore the previous day's snapshot, takes about five minutes. Not sure why you say ext4 doesn't work as it does. Haven't tried the other programs that you talked about

I do a Syu almost every day, I also do a Timeshift snapshot every day. So if ever something is broken I can just boot into TS and reinstall yesterday's working system. Then I read the forums. That way I can see what breaks the system Only ever needed to that twice because of Nvidia updates (I'm running a very old card)

I went from Manjaro to Arch. Installed by command line (took a few tries to get it done... ) I tried their installer but it wasn't very good. Have also run Endeavour on a second pc for a while but I prefer pure Arch.