I also have 64GB on my work T480 (non-s) despite "max" being 32GB.
The Lenovo-reported max RAM specs often do not take into account newer larger memory modules released after the laptop (or at least I believe this is the reason for the discrepancy).
Even Intel says it can maximally have 32 GB of RAM.
It may require some ACPI trickery, but it absolutely is doable. If the firmware guys are super lazy it may just work without ACPI trickery.
Check out an example here: https://www.downtowndougbrown.com/2019/04/adventures-of-putt...
I have also put a NVMe in the WWAN-port, I found out that the Transcend MTE452T (TS512GMTE452T) has the right M.2-port (B+M), and it is a compatible NVMe-drive and not a SATA-drive which some of the disks of that form factor is.
