if you're talking about the server, there's a build workflow for arm64, get your binaries from the artifacts: https://github.com/openmultiplayer/open.mp/actions/workflows/build.yml?query=branch%3Amaster
keep in mind all the plugins and components you use need to be recompiled for arm64, and all of them aren't readily available in an arm64 release
if you're talking about the game, you're out of luck for now