FYI the release 2.222 and therefore the new LTS line may start breaking tests that exercise REST API features due to the enforced CSRF protection[1]: Responses to POST requests will be 403 without a valid CSRF crumb.
Tests like that should be changed to enable authentication in Jenkins if they don't, and authenticate HTTP requests using an API token instead of a password. Doing that is the preferred approach to using REST APIs since 2.96. A short-term alternative to just make tests pass (but less relevant to how Jenkins is actually used) would be setting the system property hudson.security.csrf.GlobalCrumbIssuerConfiguration.DISABLE_CSRF_PROTECTION to true before Jenkins is started.
1:
https://jenkins.io/changelog/#v2.222