The latest firmware of the MindSphere MindConnect Elements can be found in the SIOS (Siemens Industry Online Support) web-portal:
• MC IoT2040: https://support.industry.siemens.com/cs/document/109745562
• MC Nano: https://support.industry.siemens.com/cs/document/109745561
An installation guide can be found in the "Getting Connected to MindSphere documentation" in the chapter "Firmware update":
In general, there are two different ways to perform a firmware update:
• Manual firmware update of MindConnect Element
• Firmware update in Asset Manager
The necessary steps can be found in the linked documentation.
The Azure Firmware version named SP28 is in testing phase right now and will be available soon.