(Very new to Linux) dnf alternative so I can download a specific repo?
Title. What I seek is not rpm-ostree but is on Fedora. What do I do?

copr command instead of dnf copr.repo file in /etc/yum.repos.d/ and then turn off the gpgcheck in the repo filerpm-ostree will have the reporpm-ostree install /path/to/rpm.rpm
coprdnf copr.repo/etc/yum.repos.d/rpm-ostreerpm-ostree install /path/to/rpm.rpm