Multiplexed?
Rockchip’s current SATA implementation is confirmed to support SATA port multipliers even with FIS-based switching so combined with an el cheapo JMB575 you can connect five SATA devices to the single SATA adapter in the M.2 slot.
And honestly I would rather put all my disks behind such a JMB575 PM than using any storage peripherals behind an USB3A receptacle (probably the worst connector ever invented): Quad SATA Hat Disconnects - #5 by tkaiser 