This repository contains OpenRGB's i2c-piix4 and i2c-nct6775 drivers packaged as a DKMS kernel module. The i2c-piix4 driver supports the secondary i2c controller on several >= X370 AM4 mainboards.
You can get releases for Fedora, RHEL, CentOS, OpenSUSE, and OpenMandriva from my Copr.
If you wish to use this with Secure Boot, follow this guide.