This repo auto-generates .lsrules for Little Snitch and publishes them as Github Gists daily. You can subscribe to these gist files in Little Snitch. Just add the raw gist urls listed below as subscriptions to your Little Snitch.
List of generated rule files
Microsoft Teams ruleset generated from Microsoft's provided endpoints list. Caveat: after I applied these rules, I still had to deal with a couple of additional endpoints, not sure why, but hopefully this eliminates most of the annoying popups without allowing all outgoing connections. Any "optional" endpoints are allowed to avoid too much noise.