According to https://pulsar.apache.org/contribute/release-policy/#supported-versions @Lari Hotari Hi Lari, is 3.0.17 the final release of the 3.0 LTS version? Is there a chance to extend the support period of the 3.0 LTS version branch?

Pulsar project decisions are made on the dev mailing list so it's possible to suggest it. There are multiple options. the lightest approach is to just backport severe security fixes to branch-3.0 and assume that users would build their own releases.