Hi ant_oco,
As far as I know, after you configured Yammer network to only allow login from specific IP address ranges, if any user attempts to login from a browser that is outside the specified range you have set, they will not be able to access the network.
Flow accesses data from Yammer only with connections, if your network cannot access Yammer, then Flow cannot get the connection, which means that you will failed to create a Flow interacting with Yammer. In that case, my personal opinion is that you don’t need additional setting in Flow to limit it to interact with Yammer.
In addition, Flow doesn’t have such built-in setting as Yammer to restrict the network’s IP range so far. If you want to submit your feedback, you are always welcomed to tell us what you think in our Flow Ideas Forum:
https://powerusers.microsoft.com/t5/Flow-Ideas/idb-p/FlowIdeas
Best regards,
Mona Li