One unexpected quirk, no real fault of the new notebook:

Linux uses 259 as the MAJOR device number for the new NVMe drive. That value is too large for the 8-bit dev/rdev fields used by really old 32-bit binaries on Linux, so the stat(2) syscall fails with -EOVERFLOW. This breaks my ancient copy of Wordperfect For Linux (don't ask).

So I ended up hacking an exception for Wordperfect into my custom kernel. Could probably fix it more neatly with an LD_PRELOAD library of some kind. Later.