hmm, let's try putting 'latest' back?

.evergreen/config.yml

@@ -1273,7 +1273,7 @@ buildvariants:
     matrix_spec:
       auth-and-ssl: ["auth-and-ssl", "noauth-and-nossl"]
       ruby: "ruby-3.2"
-      mongodb-version: ["7.0", "6.0"]
+      mongodb-version: ["latest", "7.0", "6.0"]
       topology: ["standalone", "replica-set", "sharded-cluster"]
       os: rhel8
     display_name: ${auth-and-ssl} ${ruby} db-${mongodb-version} ${topology}
@@ -1283,7 +1283,7 @@ buildvariants:
   - matrix_name: "mongo-recent"
     matrix_spec:
       ruby: ["ruby-3.2", "ruby-3.1", "jruby-9.3"]
-      mongodb-version: ["7.0", "6.0"]
+      mongodb-version: ["latest", "7.0", "6.0"]
       topology: ["standalone", "replica-set", "sharded-cluster"]
       os: ['rhel8']
       # There is no latest for ubuntu2204, so we can't test it here.
@@ -1298,7 +1298,7 @@ buildvariants:
   - matrix_name: "mongo-recent-arm"
     matrix_spec:
       ruby: "ruby-3.2"
-      mongodb-version: ["7.0", "6.0"]
+      mongodb-version: ["latest", "7.0", "6.0"]
       topology: ["standalone", "replica-set", "sharded-cluster"]
       os: 'rhel8-arm'
     display_name: "${mongodb-version} ${os} ${topology} ${auth-and-ssl} ${ruby}"

.evergreen/config/standard.yml.erb

@@ -37,10 +37,6 @@
   # A few of the most recent MongoDB versions
   actual_and_upcoming_mdb = %w( latest 7.0 6.0 )
 
-  # FIXME: RUBY-3400, DRIVERS-2816 -- test failures on latest, so
-  # let's just silence latest for now.
-  actual_and_upcoming_mdb.delete 'latest'
-
   recent_mdb = %w( 6.0 5.3 )
   latest_5x_mdb = "5.3".inspect # so it gets quoted as a string
 %>