How can I send a private extension made for my friends only?

So I have an addon that is made for a website that we don’t want the public knowing the domain to. When uploading my extension, I selected the private version but now if I send them the https://addons.mozilla.org/en-GB/firefox/addon/extName/ url, it says

Oops! We can’t find that page

https://extensionworkshop.com/documentation/publish/signing-and-distribution-overview/#distributing-your-addon

Sorry if this is a silly question. But from my understanding there is no fuctionality like the chrome store, where you could upload the extension on AMO but the extension not be searchable, but still be accessable via url.

Thus the old solution is to self host correct ?

Correct, we don’t support those kinds of listings. Self-hosting is the alternative we offer.