Yes, you can stack a C9300-48H with a C9300-48UXM. The Cisco Catalyst 9300 Series switches are designed to be compatible with each other for stacking purposes, regardless of their specific models. This includes the C9300-48H and the C9300-48UXM.
Ensure that the Cisco GLC-TE SFP+ modules you're using are indeed fully compatible with the CBS350 for stacking purposes. While they may work as normal ports, stacking sometimes requires more specific modules.
