https://[SquaredUpServerName]/SquaredUp/drilldown/scomobjects?config={%22scope%22%3A{%22classId%22%3A%22cb5a31fe-96e7-2e4b-5f42-bded7b177f5b%22%2C%22groupId%22%3A%22%22%2C%22criteria%22%3A%22%22}}
I’m surprised it is not shared and known about more.
I would like to see last month’s SLA, not just the last 30days
Can you post a picture of the SLA you’re looking at? The link you shared doesn’t work for me. 
If you’re using 5.7.0 or later you can now use ISO 8601 durations in the Matrix column JSON. So you can change the 30 Day SLA to a month by changing Last30Days to P1M as shown in the screenshot below.
This screenshot is from a Matrix tile on a dashboard. To do this for a DA drilldown then you can modify the row perspective for DAs (\User\Packages\Everyone\perspectives\rows\distributed-application.json) in the same manner.
You may need to give Dashboard Server some time to pick up the change to the file, or alternatively either click the reload button under Reload All Content in system → dashboards or restart the app pool if you want it to take effect immediately.
An alternative is to create your own row perspective with a higher rank in the same folder as distributed-application.json. There’s a bit of background on row perspectives available in this KB article: How to create and modify row perspectives.
The JSON configuration for each possible cell, and the timeframe options for cells (including the use of page/dashboard timeframe rather than a fixed timeframe for the cell) are described at the bottom of this KB article: How to use the Matrix tile
