It appears your answer is yes; the 9148-S can support trunking.
Source: https://www.cisco.com/c/en/us/products/collateral/storage-networking/mds-9148s-16g-multilayer-fabric-switch/datasheet-c78-731523.html
Highlights;
High Performance ISLs - Optimize bandwidth utilization by aggregating up to 16 physical ISLs into a single logical PortChannel bundle with multipath load balancing.
Ports - Available in a 12-port configurable base or as a bundle with all 48 ports enabled
Performance - PortChannel: Up to 16 physical links
Try this command: show port-channel compatibility-parameters.
Have you tried creating a trunk? Any errors? It may need the 'feature' enabled. Now, a port-channel doesn't exactly mean trunking (to some) but if you are using that switch and it uplinks to core then its usually used as a port-channel assuming the Firber-channel connections need multiple vlans to traverse northbound.
