Knot Resolver still wasn't built in EPEL8, because of missing devel packages of dependencies.
FEDORA-EPEL-2020-66f83d1145 has been submitted as an update to Fedora EPEL 8. https://bodhi.fedoraproject.org/updates/FEDORA-EPEL-2020-66f83d1145
FEDORA-EPEL-2020-66f83d1145 has been pushed to the Fedora EPEL 8 testing repository. You can provide feedback for this update here: https://bodhi.fedoraproject.org/updates/FEDORA-EPEL-2020-66f83d1145 See also https://fedoraproject.org/wiki/QA:Updates_Testing for more information on how to test updates.
FEDORA-EPEL-2020-66f83d1145 has been pushed to the Fedora EPEL 8 stable repository. If problem still persists, please make note of it in this bug report.