I have tested upgrading from 2.277.4 to new LTS 2.289.1. I do NOT see this problem resolved:
2021-06-15 16:05:52.766+0000 [id=27] INFO hudson.PluginManager#loadDetachedPlugins: Upgrading Jenkins. The last running version was 2.277.4. This Jenkins is version 2.289.1.
2021-06-15 16:05:54.865+0000 [id=27] INFO hudson.PluginManager#loadDetachedPlugins: Upgraded Jenkins from version 2.277.4 to version 2.289.1. Loaded detached plugins (and dependencies): [sshd.hpi]
Contents of jenkins.install.InstallUtil.lastExecVersion after upgrade:
$ cat jenkins.install.InstallUtil.lastExecVersion
Please confirm the fix was actually released for LTS.