The product specifications reference or PSREF is the usual place to compare Lenovo stuff - Oddly enough, you can't filter the operating system section for the Ubuntu options (product codes 30BFS6EL00, 30BFS76F00, 30BDS4T000, and 30BDS4T100 for various combinations of an NVidia RTX 6000/8000 and dual/single socket processors):

https://psref.lenovo.com/Product/ThinkStation/ThinkStation_P...

http://psref.lenovo.com/syspool/Sys/PDF/datasheet/ThinkStati...

But they don't even include a Windows option with matching graphics cards.