Thanks for the info. We've moved some capabilities of the Deployment Monitor App into the platform, namely the License Usage/Report. See this. I would also suggest looking at the S.o.S "Indexing and Forwarding" views that allow split-by Forwarders.
For now unfortunately, a lot of the Forwarder-centric views/alerts that were in Deployment Monitor don't have an equivalent as we wind down support for Deployment Monitor but we are working on it actively. The Forwarder Management view (viewed in Settings on your Deployment Server, if you use Deployment Server) will give you some insight, a bit differently albeit than the "Missing Forwarder" alert in Deployment Monitor, about which Forwarders were talking to your Deployment Server instance but have ceased phoning home. See this. Definitely acknowledge this is a less active approach than an email alert.