Hi @Peter Samuelsson ,
this is a very interesting challenge, one I don't see often. Since the SQL Replication MP uses the same Run As profiles as the standard SQL MP, using those might not be a good idea.
And yes, you are right, the use of Service Security Identifier (SID) or Local System account as the Run As account is not supported in the management pack.
Now, because this is a grey teritory I would recommend seeking help from Kevin Holman by postging the question under his blog:
SQL MP Run As Accounts – NO LONGER REQUIRED
https://kevinholman.com/2016/08/25/sql-mp-run-as-accounts-no-longer-required/
I see that he generally replies, so you might just get an answer from him.
If I had the same challenge, I think I would configure a domain account, add it to the profiles and distribute it to all SQL Servers, which are participating in the replication. Also, add the required permissions on all monitred SQL Instances, so that the standard SQL monitoring can also succeed.
So on all SQL servers, which are doing replication, instead of the HS SID I would use a domain accont, thus being able to monitor both SQL and SQL replication.
I hope this helps you out.
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Regards,
Stoyan