How to upgrade or add an SSD to Lenovo's Legion 5i 15 - TECHTELEGRAPH
Lenovo Legion Y520-15IKBN Hard Drive Replacement - iFixit Repair Guide
Lenovo Legion 5 SSD upgrade. : r/AMDLaptops
Yes, Legion 5 Pro has two NVMe PCIe 3.0 2280 SSD slots, the second slot is empty and has a pre-installed heatsink with a thermal pad. (I installed Samsung 970 Evo 1TB