FYI, I’ve lost data with a NAS on two occasions in the past.
In the first case, after a drive failed and before it could be replaced a second drive failed.
(Later found out all the drives were purchased at the same time and from the same production run and subject to the same manufacturing flaw).
In the second case, after a drive failed and a replacement drive inserted, the extreme load created by the rebuild (scanning the entire array and re-calculating the parity data, and writing it back to all the drives), a second drive failed.
After that, I always configured the NAS for RAID 10 which provides protection against two drive failures, but is much more expensive as more drives are needed for lower total usable capacity.
That may be the reason we focus on NAS systems. My main computers currently need 4-6 TB to fully backup. The NAS system has a BU of stuff that is well over that in size.
Our local disasters are typically wind, rain and snow events. And we do have backups in multiple locations. IF we flood there is a lot more going on, we’re over 600 feet up from the river.
How long ago did online backup start become practical? Around 2005 - 2010? Offsite was all we had before high speed internet. You can’t backup much on 56 kbps leased lines.