Judy-devel is not available in epel8 which is now a dependency for netdata
Unfortunately since Judy is packaged in the AppStream repo, I can't built it for EPEL. There is a common issue of missing -devel packages in EL 8.0. https://pagure.io/epel/issue/92
Judy-devel is now part of the CRB (code ready builder) repository of RHEL 8. EPEL Build is now neither needed, neither possible (guidelines).
For the record: It was part of this errata for RHEL8: https://access.redhat.com/errata/RHSA-2019:3708