Looks like in https://src.fedoraproject.org/rpms/dnf/c/8d1c31a72daad1689ebbed9e4983943432eb9822?branch=master dependencies between python3-dnf and deltarpm has been changed again from weak (Recommends) to fixed (Requires).
PR https://github.com/rpm-software-management/dnf/pull/1103 and https://src.fedoraproject.org/rpms/dnf/pull-request/10
The issue is solved by dnf-3.0.1-1 that was released into rawhide.