BEWARE: Lenovo Thinkpad L15 Gen3 SSD is practically un-upgradeable. Laptop comes with 256GB and bigger SSD is too thick to fit. There also goes a cooling plate on top. : r/thinkpad
Lenovo ThinkPad T14 Gen 4 Intel® Core 13th Gen i5-1335U, 16GB DDR5 RAM
How to upgrade the RAM and SSD on the Lenovo ThinkPad X1 Extreme