The reason I went RAIDZ2 in my current setup was because of the number of disks increasing the chance of multi failures. But with fewer disks that goes down. I'm not at all worried about data loss, as I said I have good backups so I can always restore. So if the remaining disk dies during a rebuild, that's unfortunate, but it only affects my uptime, not my data.
That's the exact opposite of my experience, if we're talking anecdotal evidence. I've had 3x WD Red drives die within the warranty period,so thankfully I wasn't out of pocket, but I now avoid them. Never had a Seagate go bad, but my goto is now Toshiba.
I moved from a Drll R710 with dual docket Xeons to a rack mount desktop case with a single Ryzen R5 5600G. I doubled the performance and halved the power consumption in one go. I do miss having idrac though. I need a KVM over IP solution but haven't stomached the cost yet. For how often I need it it's not an issue.
I have some scripts that use restic to backup to locally connected USB drives weekly.
The USB drives are connected to smart plugs that I control via home assistant and some webhooks. So the drives are off and stay off when not in use for the backup. I also don't turn them both on at the same time.
I bought an Odroid HC2 years ago with the intent to have it connect over wireguard and mount to the NAS VM. Then I could put it in a friends house and use it as an offsite backup.
I have Unbound and a pihole. Started with just unbound but found I needed device specific rules that I couldn't do. So I setup pihole and some devices use that as published through the DHCP. Things like the Mrs didn't want certain ad blocking on her devices, but I did everything else. Also means in future I can block more just on the kids devices.
Just get a cheap old office PC from eBay or local market place for £50. Add your disks using ZFS (don't use raid as it basically doesn't work in modern systems). I'd be tempted to get one 4tb internal drive and one external usb to use as your backup drive.
Lots of good suggestions so far, Brave New World and Don't Look Up would be right up there for me. But my #1 is this...
The Machine Stops (PDF)
Written in 1909 so out of copyright, this book is so ahead of its time it makes remarkable reading today. The amount of things predicted that describe the modern day is incredible. It's also not that long, so well worth a read.
I know everyone tries to avoid this and I'm sure you're trying to learn on the cheap like everyone else, but honestly, get a few lessons with a good local tutor. You'll learn more from them in a few short hours than you will with months of trying to do it yourself.
Famous guitarists never seem to say how much hard work went in to perfecting their craft, but it is a lot. And all the good ones took lessons and some still take lessons even though they're on international tours and have sold millions of albums.
Can't think of anything too outrageous. I have a 24U server rack in my garage which fits with mm perfection under the stairs.