The solution to this proved quite simple, once I grasped the fact that all routers on a common network have to route for that network (duhh!!!) as well as any others that they may handle.
So the ripd.conf file looks like this:
---> ! -*- rip -*- ! ! RIPd configuration file ! hostname a.b.domain.tld password xxxxxxxx enable password xxxxxxxx
router rip network 2aa.bbb.ccc.0/24 network 192.168.219.0/24
log stdout <---
And it works.