There are plenty alternatives to Open-Registry, probably the most famous is the npm registry by the company npm inc.

Most differences in the listed alternatives is about performance and governance.

For performance differences between the different registries, please look at the benchmark results from https://github.com/open-services/public-registry-benchmarks

Name Governance Geographic Location
Open-Registry Community Owned EU
npm Registry For-profit Company US
node-modules.io Registry Individual US
cnpmjs.org Registry Unclear China?
js-ipfs Registry For-profit Company US

In general, it's easy to switch to any alternatives on this list. Simply run npm config set registry $registry-url in your terminal, replacing $registry-url with the URL to the registry.