Hi,
Maybe, it is possible to have the same approach as when you monitor oracle databases in Oracle cloud when you cannot install the agent on the db server.
See this blogpost
Monitoring Oracle databases with Checkmk | Checkmk and Step 6.
There they suggest a piggy back host where you install the agent and the sql server driver and the sql server plugin.
I haven’t tried it myself, but I have it in mind since we have a lot of customers using oracle cloud and some are starting to think about managed dbs in the cloud and that’s the same situation as Azure Managed Instance since you cannot install the agent on the db server.
/r