OpenMandriva. It is the official successor from Mandrake/Mandriva and has a rolling release edition called ROME which has brand new software. It is independent too and does not belong to a corporation.
We are looking for developers, packagers, translators, supporters. If you are interested come and join our Matrix chat :)
DNF and RPM, yes. You can usw zypper too. There is also a znver1 Architecture Edition optimized for the Zen/Ryzen CPU architecture.