We’re working to bring back the ability to embed gadgets in Confluence in a Marketplace app. While the app is still in development, we’re sharing it with you for testing. Download the app using the link below and use it test your workflows and gadgets in the new environment.
The app is still under development and its functionality may be limited.
We performed a first set of tests with this new app (build 100.0.3) on Confluence 9.2 in combination with our apps from the Atlassian Marketplace and everything worked perfectly! 
Our tested apps were:
Testing was performed on both a freshly installed Confluence 9.2 instance and an instance upgraded to Confluence 9.2.
I can confirm that after installing this app on top of Confluence 9.2 the “External Gadgets” section becomes available again in Confluence Administration area, the old gadget feeds (added before Confluence upgrade) are kept, and the app macros (added to Confluence pages before and after upgrade) are fully functional.
Thanks for this turnaround!
When should we expect this app to be officially released on the Atlassian Marketplace?
Danut.