Based on Revision 74 of original filter-dkimsign at http://imperialat.at/dev/filter-dkimsign/
NOTE: libopensmtpd must be install first.
# Make sure these are installed first: make gcc mandoc
sudo dnf install make gcc mandoc
make -f Makefile.gnu
sudo make -f Makefile.gnu install
# You can remove rpms you installed: sudo dnf erase make gcc mandoc
filter-dkimsign -d domain.com -D -k keyfile -s selector
Here, domain determined from From: header will be used in DKIM signing. If domain from From: header cannot be determined, then it will fallback to domain.com (the argument of -d)
The benefit of using -D option is that you do not have to specify -d option 100 times, assuming you have 100 domains.
CAUTION: If you use -D option, first make sure that domain (used in From: header) has DKIM configured for it in DNS properly. Otherwise mail can bounce (unless your domain has proper DMARC configuration and your SPF alignment succeeds)