https://wccftech.com/ps5-firmware-update-to-enable-ssd-expansion-this-summer/

The ability of SSD expansion built into the PlayStation 5 was unveiled almost a year ago by System Architect Mark Cerny. Sony, in fact, did add an NVMe M.2 port for this specific purpose, but when the console launched in November, we learned that it would not be active for the time being; a later firmware update would actually enable the SSD expansion. Right now, if you try to insert an NVMe SSD through the M.2 port, the PlayStation 5 doesn't boot anymore. Of course, technically you can also connect a USB hard drive in order to exploit additional storage capacity, but that only works for PS4 games working through backward compatibility.

A new report published today by the Japanese version of Bloomberg suggests that update is on its way and scheduled to hit at some point this Summer. The same firmware update should also 'improve the rotation speed' of the console's cooling fan. This will be needed to avoid any potential overheating issues once users add an extra SSD into the console.