They’re repos maintained by a single person, and official documentation tells you to avoid them, cause their purpose is to be a place where maintainers can break unimportant stuff.
If something is only available through community repos, the official way forward would be to submit a bug report to OpenSUSE, asking to include the package in the official repo, or to contact the maintainer and ask them to do it.
I’d keep use of community repos to a minimum and prefer first flatpak, then the experimental repo over them. No one but the maintainer themselves checks or tests the community repos for stability and compatibility.
But I’ve activated one community repo for a package that wasn’t available anywhere else (sane-airscan).