I’m the same as you - I had experience with mdadm, LVM, LUKS, and ext4, but no experience with ZFS. I still don’t know a lot about ZFS, but Unraid set it up for me, and I can always Googl4/DuckDuckGo any issues I encounter.

From what I can see bit rot is not a huge problems for home users

The thing is that it’s likely that lots of people are affected by bitrot and just don’t know it, since there’s no way to detect it without using checksums. People don’t know that their files have succumbed to bitrot until they try to use them and realise they’re corrupted.

Instead of 4 x 6TB drives, consider 2 x 14TB or even 2 x 20TB in a ZFS mirror. Buy the biggest drives you can afford that have reasonable pricing. When I was buying drives two years ago, 16 - 20GB was the sweet spot for price per GB.

Make sure you use NAS drives. Western Digital has had several controversies so I usually go for Seagate Exos instead.

You could use an OS like Unraid that handles ZFS for you. You don’t really need to know how ZFS works if you use Unraid since it’s all set up through the web UI. You can always search for how to do things if needed :)

ZFS has bitrot protection which is very useful for important files. Whenever you save a file, it computes a checksum for that file and stores it in the file table. When you read a file, it can detect if that file is corrupted on the drive it’s reading from (the checksum won’t match) and it’ll silently / automatically repair it using data from a different drive.

AFAIK none of the other file systems support this. You need to use ZFS RAID rather than mdadm RAID for it to work.

Check Usenet, or get a friend with a subscription to a Usenet indexer to search for you.

Keep in mind that software doesn’t have an expiry date. If a piece of software is unmaintained and doesn’t have an active fork but it still fulfills your use case and doesn’t have any major issues, there’s no need to replace it. Some of the software I use hasn’t seen any updates in five years but I still use it because it still works.

Edit: As an example, a lot of people still use WinDirStat even though the latest release 1.1.2 is now 17 years old.