Photo Backup Project Update since I'm about to close the 2nd full week.

Two of SanDisk's 4TB SSDs were DOA or well dead on arrival after accepting my copy of 2.5 terabytes of photos to them. Turns out there's a known issue this week - https://arstechnica.com/gadgets/2023/05/sandisk-extreme-ssds-keep-abruptly-failing-firmware-fix-for-only-some-promised/

I did not read this article before buying them but lost no data.