How to install repmgr 4.2 (ubuntu) apt-get install postgresql-10-repmgr  give me repmgr 4.3.  However, my primary server is still on 4.2.

How do I install repmgr version 4.2?

Thanks in advance!
An archive of old packages (3.3.2 and later) for Debian/Ubuntu-based systems is available here:
http://atalia.postgresql.org/morgue/r/repmgr/