Can we register an existing site collection as a Hub site

Question

I am reading this official Microsoft documentation SharePoint classic and modern experiences, which mentioned that there is not a 1:1 map between site collections and hub sites, and we can not move a site collection to a hub site:-

There is not a 1:1 mapping between site collections and hub sites, so you can't automatically move a site collection to a hub site.

But on the other hand, there is another Microsoft official documentation, which mention how we can register a site collection as a hub site Register-SPOHubSite. so i got confused..So if we have a site collection (modern or classic) which contain data and lists, can we define it as a hub site?, that other site collections can link to? as the info in the above 2 links is confusing, unless i did not understand it well.

Thanks

Answer 1

Yes, you can convert any existing site to a hub site, refer this I was able to create a classic site, register it as a hub site. Then create a modern communication site and associate it to this hub site.

Answer 2

We can register an existing site collection as a Hub site.

Note: Sites that are already associated with another hub can't be converted to a hub site. Make sure the site is not associated with another hub.

We can create up to 100 hub sites for an organization.

Create a hub site in SharePoint Online for your reference:

https://docs.microsoft.com/en-us/sharepoint/create-hub-site