Longer term: Maybe Apache can be taught to warn users about this mistake?
If it sees that the specified certificate is signed by some other certificate and no chain is provided, it could warn that this may be a configuration mistake.
Self-signed certs wouldn’t trigger this (so no annoying warning for them)
Mozilla and/or the BRs oblige public CAs to not issue from their root, so an intermediate will always be needed (there may be old certs this isn’t true for, but not new ones) and so it’s OK to warn for almost all non-self-signed cases.
It seems as though web servers will need to learn to inspect the contents of the certificates they serve anyway, to implement things like OCSP stapling sensibly, so they might as well warn the administrator about goofs like missing intermediates, or the use of certificates which have already expired or don’t match the configured name.