To unblock T232931: Remove support for run-time automatic $wgServer default value, quibble needs to explicitly supply the value for $wgServer to the installer, using the new --server option. From the patch https://gerrit.wikimedia.org/r/c/mediawiki/core/+/524396:
Looks like the quibble jobs are still depending on this. Their generated settings are now getting "$wgServer = "http://localhost";" which is wrong (should be something like "http://127.0.0.1:9412", which I guess it needs to pass it from its ENV var).