@RustemShiriiazdanov – This is not an answer to your immediate question, but I wanted to point you to another thread in the forum:
If Atlassian Support told you this:
The key risk remains around gadget key changes between module types — if the key changes, existing gadget instances on customer dashboards may be lost.
Then that might be reportable as a valid migration blocker. (Unless someone chimes in with a positive personal experience.)