The /load_balancers/non-lb-connection-establishment JSON spec test currently fails and/or is flaky. The specific sub-test that is failing is "operations against non-load balanced clusters fail if URI contains loadBalanced=true". It produces this error:

error: expected error to contain "Driver attempted to initialize in load balancing mode, but the server does not support this mode", but got: "BSON field 'hello.loadBalanced' is an unknown field."

The test is currently being skipped, so to work on it, it will first be necessary to remove it from .evergreen/skip-tests.txt and run a patch build to determine the current failure mode(s).