Synology has backtracked on one of its most unpopular decisions in years. After seeing NAS sales plummet in 2025, the company has decided to lift restrictions that forced users to buy its own Synology hard drives.
If you want to use M.2 SSDs for your storage pool and cache, then you still need to use a Synology-certified SSD (which doesn’t necessarily mean that it needs to be Synology branded, just tested and certified).
From https://liliputing.com/synology-backtracks-and-adds-3rd-party-hard-drive-support-to-its-2025-nas-lineup-network-attached-storage/