I think I'll have to throw away all my collected USB-C cables. I just had one connected to the external SSD, which I assumed was reasonable, and the copy process should take > 4 h. Other cable connected: 6 min 🤯 Is there any way to test the cables?
There is. For example https://caberqu.com/home/20-43-c2c-caberqu-746052578813.html#/27-case-with_case as mentioned on german podcast https://freakshow.fm/fs276-remember-we-are-in-the-eighties-so-dress-accordingly
The most compatible USB-C cables currently available are probably Thunderbolt 4 cables.