ZFS with automatic snapshots and scrubbing. This will keep as many and as old snapshots as your like. It’ll ensure the files don’t rot. It’ll ensure the media doesn’t die, so long as you have enough redundancy and you replace disks as they die. This is what I’d trust for long term storage because I think I understand how and why it works. It should last as long as I feed it disks. If I delete something, I should be able to restore it from a snapshot. The hardware doesn’t need to be anything fancy. Just a Pi 4/5 with a couple of WD Elements would be fine. Could add more disks for more redudnancy. I’m running 2-disk residency.
You don’t have to touch the software if it’s not exposed to the Internet. Whatever works today on it will work 20 years from now, so long as the hardware works. A couple of spare Pis, SD cards and power supplies should let it last for decades.
Me who uses GNOME on Debian stable