Hi,
at the moment there is no SFP28 from Meraki itself, you have to take the Cisco modules. Attention, it is only supported from a certain firmware.
Small-Form Factor Pluggable (SFP) and Stacking Accessories - Cisco Meraki Documentation
*Note: The SFP28/QSFP28 modules will be orderable March 2024 with software support in CS16.7. 25Gbps Dashboard support is slated for CS17 firmware. 25Gbps optics can be used in CS16.8, but should be considered 'Beta'.
When you plan to use the active direct attached cables I would recommend to ask your Meraki sales responsible first.