When uploading a mod to Modrinth, we strongly advise against having multiple projects for a single mod. Instead, your mod should be uploaded as one project with multiple versions supporting multiple mod loaders. Projects like this can be found all across Modrinth, such as Cobblemon, Architectury API, or CraftPresence.
Having one singular project has a variety of benefits.
Consolidated downloads will make it easier for people to discover your mod. Since search and discovery is primarily weighted by download count, this leads to more people having the ability to find and use your mod.
Simpler Maintenance, since instead of having to update two project pages and all the work that entails twice or more, every time you update your mod, you only need to do it once.
Multiple Modrinth features take advantage of the fact that projects can support more than one loader. The Modrinth App and other supported launchers also take advantage of this by automatically selecting the version that's relevant to a user when they want to add your mod to an instance.
These are just a few of the advantages of keeping your mod on a single project page, making it overall much more convenient for you and for users downloading your mod.