At the same time including a wildcard at the end of the non-existent directory name with 2.4.18-2ubuntu3.8 makes apache2 happy:
IncludeOptional /etc/apache2/whatever*/*
apt policy apache2 apache2: Installed: 2.4.18-2ubuntu3.8 Candidate: 2.4.18-2ubuntu3.8
At the same time including a wildcard at the end of the non-existent directory name with 2.4.18-2ubuntu3.8 makes apache2 happy:
IncludeOptional /etc/apache2/ whatever* /*
apt policy apache2
apache2:
Installed: 2.4.18-2ubuntu3.8
Candidate: 2.4.18-2ubuntu3.8